We know the Constitution
Class still had a few years left in their service lives, there was one in the aftermath scene at Wolf 359 in BOBW (a re-use of the wrecked hull from TSFS).
I suspect the A was just a last-through-the-gate refit. This could explain the problems in V, as if they incorporated every advance up to that date, the space-frame just found it difficult to cope?
That would mean that new-construction ships would be fine as they could be 'future-proofed', but the older refitted ones just could not be advanced any further, hence why a relatively new ship would be decommissioned.
As to a surprise, it was to me. I too was convinced they'd just get handed the Excelsior