[SamBam]

Hmmm, is the second definition here [1] the "screwed up" one?

> An issue regarded as potentially debatable, but no longer practically applicable. Although the idea may still be worth debating and exploring academically ... the idea has been rendered irrelevant for the present issue.

That's literally the only way I've heard it. (American here.) I'm nonplussed about this.

1. https://en.wiktionary.org/wiki/moot_point

[lupire]

"The second usage given is modern and is the meaning more commonly understood in American English, possibly because of the association with moot court."

"Up for debate but not decided yet"

"Debatable, but decision doesn't matter".

It's a natural ambiguity, resolved by context, one of many, many in language. Which one is correct is a mute point.