I think everyone is missing the forest for the trees, or maybe missing the tree for the forest? Anywho as I said earlier...
"All we know is that “Constitution” was one of the Enterprise’s sister ships listed in TMoST, and that “STAR SHIP MK IX/01 CONSTITUTION CLASS” was on the phaser schematic that Scotty was viewing in "The Trouble with Tribbles". Trimble probably just put two and two together and drew the obvious conclusion?"
There is no contradiction between fandom and canon here, "starship class
" and star ship
MK IX/01 (Constitution) class
are synonymous, and one is merely the abbreviation of the other. Both merely designate a capital ship of the line.
As for "Constitution"
, since it's one of the (12) ships like the Enterprise (i.e. Enterprise class, so to speak) given in "The Making of Star Trek" (based on intra office memos) it's clear beyond a reasonable doubt that the phaser diagram is depicting phasers for ships like the Enterprise and her sisters, and that those in the production intended this to be so.
In brief, “STAR SHIP MK IX/01 CONSTITUTION CLASS” is the complete and correct designation for which
" and “Constitution class” are both interchangeable shorthand for.