Well, for decades, all of fandom assumed that ships were supposed to have different insignias. There are plenty of in-universe reference books, comic books, and fan films depicting conjectural insignias for other starships, and multiple books putting forth the idea that the arrowhead insignia wasn't standardized until shortly before ST:TMP -- the usual line being that it was adopted fleetwide to honor the Enterprise, which I think is pretty disrespectful to all the other accomplished Starfleet crews that must be out there. Essentially, fandom ignored the "Court-martial" evidence altogether. (Well, mostly. I think there was one fan reference book I knew of that treated the insignia as representing different fleet divisions rather than individual ships, similarly to how I'm treating the 2160s Starfleet insignias in my Rise of the Federation novels.) But now we have Voyager's "Friendship One" showing the arrowhead as a UESPA logo in the 2060s, we have Enterprise including a teeny version of the arrowhead on enlisted crew's rating patches, we have the Abramsverse showing the insignia in fleetwide use in the 2230s and '50s, and we have the Justman memo proving it was meant to be that way all along. So the old belief has been pretty thoroughly overwritten/discredited by now.