And the Ent-A used the Ent-D's engine room set in TUC, even though it obviously wasn't supposed to be the same design. I was referring more to the outward appearance of the ships.
Actually, the Enterprise-D's engine room set was the heavily updated/modified version of the TMP Enterprise's engine room set. They simply didn't have time/money to convert it back, esp. with TNG still in production at the time.