Somehow, fans popularly remember that but very little of the other stuff he considered apocryphal - like almost all of TOS
("I have never been so foolishly heroic as depicted..." he writes as Kirk in the TMP novel, backed up by interview comments from Paula Block here
. That link also has a quote from Roddenberry saying Wrath of Khan
"is not Star Trek") and I read somewhere that Gene also felt the same about VI as he did V, believing that Starfleet officers were beyond things like racism (apparently "Balance of Terror" is especially apocryphal) but I can't find that quote right now.
This is why I'm glad GR never got to officially pick and choose which episodes/movies count and which don't. The guy seemed intent on reimagining the Trek universe, at the cost of what made it great in the first place.