It's simplest when people say "I think" when expressing an opinion rather than saying it as if it's factual. It saves all the arguing.
A quote from Roddenberry would be good, but until others can confirm it by seeing/hearing it, it's not a primary source.
And, anyway, unless someone finds an old memo from the Desilu days that addresses the name change, then there will always
be doubt about the actual reason, especially since Roddenberry's stories tended to change, and memory is fallible. (Aside: Speaking of internal memos, one of the TOS ones reveals the origins of the TAS life support belts.)