Flynn had enough pecadilloes that were well-known. There was really no reason to make up new ones. he's another of those "stars" whose real-life persona is blurred with his onscreen ones. We always think of him as a swashbuckling hero, when in reality, he was a drunken, drug-using skirt-chaser who liked teenage girls. He is another example of why it may be best not to know everything about a movie star.
I've read Flynn's auto-bio, and if he wrote it, which seems likely or at least hasn't been disproved, he was a fairly intelligent guy. And one of the few Hollywood tough guys who really was tough in real life. He beat the snot out of Hollywood tough guy character actor Gwyn "Big Boy" Williams after Williams insulted Flynn on-set during one adventure flick filming.