I sort of agree with Neverar, I don’t really think the Jedi having an official age limit undermines the line in the OT. It’s still really dumb, though, and it feels like it’s a gross misinterpretation of the line in ESB, especially because Lucas was not the one who wrote it.
It is very likely that Lucas wrote the original premise for the line in the second screenplay draft. Of course, the final line was written by Kasdan, but I doubt the idea was not already there in Lucas’ second draft.