I'd agree the Cubs probably don't care about a salary dump, although EVERY owner pays at least a little attention to the bottom line.
However, Bellinger's contract with the Cubs includes a mutual option for 2024, which I'm reasonably certain prevents the possibility of a QO. The Cubs can't decline the option, then make a QO.
It also means there's at least a chance Bellinger is here for 2024 too.
And if Buxton isn't gonna play CF, they need better than MAT. Bellinger's huge year came in 2019, so it's a little suspect, but it was a 1.000+ OPS MVP year.
https://www.baseball-reference.com/players/b/bellico01.shtml