Does the rule of sequence of tenses sacrifice some degree of information recover...

Suppose that originally a sentence has a matrix clause in the simple present tense and a subordinate clause in the past perfect tense. Then, if I stand at a point in time after the event described by the matrix clause and retrospectively report this sentence, the matrix clause can be shifted into the simple past, while the subordinate clause must remain in the past perfect.

Now suppose another sentence originally has a matrix clause in the simple present tense and a subordinate clause in the simple past tense. If I again stand at a point in time after the event described by the matrix clause and retrospectively report this sentence, the matrix clause can also be shifted into the simple past, but the subordinate clause will now be shifted into the past perfect.

Therefore, when additional temporal expressions and other contextual temporal information are relatively limited, we face the following problem: because two subordinate clauses that originally had different tense forms are mapped onto the same tense form after the matrix clause is shifted into the simple past, the past perfect in the retrospectively reported sentence may correspond to two different possible original tense states. Consequently, when we attempt to reconstruct the original temporal information in reverse, we encounter ambiguity. In other words, this process does not have unique recoverability at the syntactic level.

I am not sure whether the following two pairs of sentences can illustrate the idea intuitively:

Original state

A. I know that he had left before I arrived.

B. I know that he left yesterday.

Retrospective report from a point after the time of the matrix clause

A'. I knew that he had left before I arrived.

B'. I knew that he had left yesterday.

In other words, there seems to be no way to avoid this problem purely through grammar. To prevent this loss of information, we would need to supply additional temporal information, such as explicit time expressions or contextual cues.

(This is a question, not merely an observation. If you agree with my point, could you provide relevant literature to show whether there is scholarly support for this view? Conversely, if you disagree, please cite sources that challenge it.)

P.S.

If expressed in more abstract and rigorous terms: the rule of sequence of tenses is not an injective mapping because there exist different original tense configurations that are mapped onto the same resulting tense configuration. Since such a mapping does not satisfy the necessary condition for having an inverse function, it lacks an inverse mapping. Therefore, the original temporal information cannot be uniquely recovered.

Incidentally, this problem may become even more apparent when analyzed within Reichenbach’s theory of tense, since the temporal relations between Speech Time (S), Reference Time (R), and Event Time (E) provide a more explicit representation of the information that is lost during tense shifting.

Jespersen agrees that the preterite perfect (your past perfect, Jespersen's plupferfect) could correspond to multiple original utterances.

The pluperfect cannot be further shifted: "I had already seen her before she bowed" becomes "he said that 'he had already seen her before she bowed". The indirect "had seen" thus corresponds to three direct tenses, saw, has seen, and had seen.

(A Modern English Grammar on Historical Principles, Part III, p151)

But there is no rule about having to backshift a preterite, and so even a simple past may be ambiguous.

The direct preterit does not always become a pluperfect: "I didn't know that you had so much money" may imply either 'I now discover that you have so much' or 'that you [then] had'; but in the latter case you had had may also be said.

The same source points out that it is less common to backshift a preterite, noting that "[b]ack-shifting generally affects those tenses only that are formed by means of the present-tense forms"

The simple preterit may be shifted [...], but this is not always the case: "There was some shooting yesterday'" may be rendered either "He said that there was some shooting yesterday" or "He said that there had been some shooting yesterday" or, finally, "He said that there had been some shooting the day before".

In fact, backshifting often causes a certain ambiguity in interpretation outside of futher context.

There is a curious use of the preterit dependent on a not expressed main verb in cases like this: Someone has told me "I am going to Bristol on Thursday". A little later I remember that he is going, but forget the date, and ask: 'What day were you going to Bristol?" or "Was it on Thursday or Friday you were going to Bristol?" (= What day did you say you were .... ).

In the above it's not immediately clear from were going whether it's the future that's intended relative to the utterance or sometime in the past, though in the context there would be no ambiguity. Also in the examples below whether all actual situations denoted by verbs in the preterite form are in the past, or whether some are yet to occur.

A present, which in a clause subjunct would mean the future time, is often back-shifted:

Shelley L 417 I promised to write to you, when I was in the humour [= I shall ... when I am ... ] | Doyle R 128 his father's wise advice that he should not think of marrying until he was a Commander [don t marry till you are ... ] | id S 1.127 I left him with the conviction that when I came again on the next evening I would find that he held in his hands the clues | Gissing H 279 Now and then he asked himself what was to become of him when sickness or old age forbade his earning even the modest income | Jameson'F 311 [prospective mother] thinking that these would not be the first things her little son saw, as she had meant them to be; and wondering what the bed would be like in which he was born.

In carefully edited prose, it's up to the writer to choose how to frame the report so that there is no confusion.