I think it's also kinda like a "that'll teach 'em!" thing. Possibly aiming at his former bandmates (and of course namely Gilmour).
"Look, I own the song's rights, so I can do whatever I want and your shitty performances should've never made it into the original in the first place!"
You can skip to absolutely every position in every tune - you'll end up with maximum embarassment.
WTF could be the reason for a "redux" version of "Great Gig In The Sky"? The only thing you can do to this maximum iconic piece is to a) copy it as good as possible for live performances (and while there's some singers really nailing it, I'd rather not touch that particular one, even if it was just to honor Clare Torry) or b) just leave it alone, documenting one of the greatest "it just happened" moments in popular music. No need to ever (re-)touch it again, it's pretty much absolutely perfect as is.
Before listening to this shocking musical desaster, I was still thinking that Waters might, just perhaps, have something to offer that slipped through on the originals. Or he might have a fresh idea on how to do things in 22/23. But nothing.
Instead, everything the original is about apart from the writing, has been eliminated. The performance and production value of this new version trends towards zero - whereas these have been elemental aspects of the original. They supported the writing and gave you the whole picture rather than a mediocre, blurred impression of whatever.
Now, one thing this new version might be supposed to demonstrate would be "see, good songwriting works without all the bling-bling".
Just that it doesn't. Not in the case of PF.
The various sonical aspects have always been a huge, integral part of PF's portfolio. Heck, there's half hour long instrumental psychedelic things only working due to their wild sound manipulations and such.
Yeah, some songs would defenitely work in an even easier setup (acoustic guitar and vocals), but PF simply ain't no Johnny Cash, hence this DSOTM rendition is no "American Recordings", either. Not even close. With Cash, it was reduction to the most necessary elements, with Waters it's a selfish parody kinda thing.
Add to this those songs where it doesn't even remotely work. "Great Gig In The Sky" simply isn't a PF song but great harmonies from Rick Wright laid out leading to an impromptu "composition" (if you will) of Ms. Torry. "On The Run" isn't a PF song, either. It's some lyrics they could only effectively use because they were fooling around with that EMS Synthi AKS beforehand.
Also, unlike the mentioned Cash, PF has alway been into whatever bigger-than-life-unheard-as-of-yet things and most memorable instrumental performances (with Gilmours parts obviously standing out, but Wright hasn't been a slouch, either, there's some incredibly great harmonies played through killer sounds). Taking these out completely doesn't do the material (and original intention, too) justice. If you wanted to do so, you'd have to come up with something else instead but the generic backings that this album is full of.
Seriously, this is shockingly bad.