Is the concept of "backshifted past tense" in reported speech applicable to other types of subordinate clauses?

Solution 1:

Could all the boldfaced verbs of these examples be subsumed under
"the backshifted preterite" as defined in CGEL?

If you want to subsume them, feel free to do so. They are all grammatical and colloquial English.
In complements -- and all of these clauses are complement clauses -- some subject complements, and others object complements -- except the last, which starts with an unbolfaced preterite-form modal (wouldn't) and continues with another (could) and a preterite in a relative clause (that was great).

Though it's not necessary to label tenses as "backshifted" or not. These are preterite, certainly.
And if one has a usable definition of "backshifted" -- i.e, a definition that can be applied to any case and will always distinguish "backshifted" forms from non-"backshifted" forms -- no problem.

However, it appears that you don't in fact have such a definition (or perhaps CGEL doesn't),
because this question is about what it means. If there's a definition, apply it.
If there isn't, the term is useless. Take your pick.

Solution 2:

On my reading of Chap. 3, sec. 6.2, Huddleston & Pullum intend that backshifted preterite is a use of the preterite that occurs almost always in embedded clauses whose matrix clause meets either of the conditions in [13i]. Its meaning is to locate the event in the subordinate clause as simultaneous to the reference time established in the matrix clause.

My hunch is that if we have to classify the OP's examples, (1) and (2) contain backshifted predicate (on H&P's definition), whereas (3) uses predicate to indicate modal remoteness. The question does makes me wonder, though, whether the predicate might fulfill both backshift and modal remoteness function in certain contexts.

Solution 3:

One problem with the concept of backshifting here is that it is based on Huddleston & Pullum's's belief, shared by many writers on tense, that "The general term tense applies to a system where the basic or characteristic meaning of the terms is to locate the system, or part of it, at some point or period of time" (H & P p.115).

Martin Joos (1960.121), The English Verb, Form and Meanings suggests that a more accurate idea of tense might be to consider the so-called present tense the actual tense and the so-called past tense the remote tense. "The latter name fits the meaning precisely. The modern English remote tense has the categorical meaning that the referent (what is specified by the subject-verb partnership) is absent from that part of the real world where the verb is being spoken."

Joos talks about two types of remoteness, in time and reality. My own work on the subject suggests three types, time, reality and directness.

Let's take your three sentences:

(1) I assumed you were the type who kept your promises.

(2) She was surprised that he still loved her.

The way people experience their iPhone has always started with the display.

(3) So we wouldn't introduce a larger display until we could make one that was great.
[These words, at 1.30 in (this video), suggest a meaning similar to "We were not willing to introduce a larger display until we were able to make one that was great".]

Let's also consider a fourth possibility;

At the moment we are not capable of introducing a larger display. This does not worry us because, even if we were capable of producing a crude large display,

(4) We wouldn't introduce a larger display until we could make one that was great.
[These words, identical to those of (3), apart from the deletion of 'so', now have a future hypothetical rather than a past-time factual meaning.]

There is no need to posit any form of 'backshifted preterite' for any of the underlined remote tense forms. In each case, the speaker/writer has chosen to make *the referent (what is specified by the subject-verb partnership) absent from that part of the real world where the verb is being spoken.