Roddenberry from what I’ve read in multiple places sounded like a huge asshole to me, and nowhere near the ‘Great Bird of the Galaxy’ he liked to self-label himself as. Now yes, a very talented asshole, whose vision started the franchise, and certainly who put in much work on TOS (along with many other talents), but nevertheless a real PITA on a personal level who wound up burning most of his bridges.
Point is-- if Meyer lost his cool with him as a young guy, I wouldn’t be very surprised.