I don’t know St.-Elsewhere, so skipping that one.
Bill’s comment can be truthful if Ron always intended the world of Monkey Island to be an amusement park - which he arguably did, according to a certain plaque.
Ron’s comment can be truthful if he always conceived an imaginary Calvin and Hobbes world, but didn’t think to reveal it at the end (and/or didn’t think to go Empire Strikes Back) until the last minute.
The disparity between Bill and Ron here can fall to a number of things. Maybe Ron always conceived the amusement park for MI1, but never intended to have it spelled out in the ending. Maybe Ron never intended the “I am your brother” and cursed voodoo eyes at the end of MI1, so that’s what he means. But meanwhile, Bill Tiller is just thinking that Amusement Park Reality = The Ending, while Ron isn’t thinking in those terms.