Exhibit B: Since we know nothing of the era outside of the novelverse, just about anything can be invented here. I got the impression from "Yesterday's Enterprise" that the Starfleet of the -C era was going through something of a budget crisis - still using the uniform and phaser designs from Wrath of Khan, and with such a spare and militaristic bridge. But then again, if the ever-changing starship designs are merely the technology-meets-art whim of future designers (as is IMO the only way to rationalize the TOS look), it may simply have been the style of the time.
Exhibit D: You're assuming a lot, here. We saw the STV phasers first in V, but for all we know (as Mr. Scott's Guide to the Enterprise
suggests about the II and III phasers) they were concurrently used designs from different manufacturers. After all, TOS-style communicators keep coming back throughout the classic movies, despite the basic design being "first" seen on the USS Kelvin in 2233. Do Starfleet keep changing then changing back? Or are they tried and trusted designs that outlive the others?