They're scaled to anime Kid Buu and other non-canon feats for supposedly following the anime, but the authors of DBM have made it clear that they're following the manga canon, going to pains to note that anything that happened in the anime but not the manga isn't canon, and they've changed the movies to better fit into the manga timeline. They discard GT with the explanation that it's "just anime" and doesn't fit in with the manga timeline.
They should be scaled to manga feats.
Given that the best destructive feat is only 4-B, this is consistent and fine. DBM has its own feats, anyways (Cooler still gets blasted into the sun, Broly flies to Earth from what used to be New Vegeta in a short span of time).
All the movies happen a lot differently in DBM (Vegeta is present during the Cooler movie, 5th form Cooler fights on par with SSJ Goku, etc). I don't remember anything being mentioned about Broly busting a galaxy, so we can't apply it.
I'm pretty sure I remember the opening literature being the galaxy being destroyed.
Without that goku wouldn't have been there and also if they point out it was different in that timeline it indirectly points to them causing devastation in the main timeline otherwise why say it's different?
I'm pretty sure that Vegito has soul destruction BTW. One of his Novel's chapter involves him meeting a guy who's absolutely, totally immortal, who can regenerate from complete physical destruction and just wants to die. Vegito learns that Hakai-ish technique specifically to give him rest.