Of course some films like Fargo (1996) went the opposite direction, claiming in the introductory text that it was "based on a true story which happened in 1987" which drove people crazy trying to figure out what real 1987 event it was based on before the Coen Brothers finally admitted that they were just messing with the audience.

When I was a kid, The Adventures of Baron Munchausen was found in the "True Stories" section of my local VHS rental.

Also took child-me far too long to realise the "Famous Historian" scene and the witch/duck trial in Monty Python and the Holy Grail wasn't supposed to be real.

My favorite "based on a true story" film is Hidalgo (2004). It's about a guy who takes a mustang horse to some multi-day desert race in the Middle East. He wins, gets a bunch of money, buys a shitload of mustangs and frees them all.

And it really happened... ish. Like, the guy the movie is based on, he did tell that story. But the actual race, never happened. There's no record of the guy ever setting foot in that part of the world. But yeah, he did tell the story in that movie.

We are beginning to realize that many of the events of Catch Me If You Can (2002), despite being based on the memoirs of conman Frank Abagnale, never happened. Abagnale was even a conman about the cons he performed.

Which is usually part of the credits and not the title screen (_before_ vs. _after_ the consumed work).

Some films put it in the opening titles. As for videogames — GTA V, for example, has "The content of this videogame is purely fictional, is not intended to represent or depict any actual event, person, or entity, and any such similarities are purely coincidental. The makers and publishers of this videogame do not in any way endorse, condone, or encourage engaging in any conduct depicted in this videogame" disclaimer on its second loading screen, right after the initial splash screen with Rockstar's logo.

Notice especially the second sentence about game makers not endorsing whatever behaviour is depicted in the game. The first sentence, by the way, is patently false because GTA Online features a character "Dr. Dre", voiced by Dr. Dre — no way it was "purely coincidental".

It's usually as the dark screen intro to the actual video. Not sure whether I've ever seen it as the end credits.

They're not obligated to do that. But lawsuits cost money.