The recon is to the timeline and initial encounter with the species
Fair enough - I'll backtrack slightly and say that if there's a retcon, that's where it is, rather than in the Gorn's behaviour.
But there is a bit of wiggle room in "Arena", I think. Kirk certainly seems unfamiliar with the Gorn, but they never really say it's the first contact, and Spock doesn't really say anything one way or the other (a very Spock-like thing to do in any situation).
They definitely have massaged that canon, but I don't think they've really contradicted it.
They're iconic for a reason.