Apparently, I have a poor understanding of Ubuntu Flavors.
I looked into this a bit in order to learn more - as in, what is included - and found an answer.
Ubuntu Flavors are Not Ubuntu Derivative Distros. They are Ubuntu with a desktop environment other than Gnome.
I apologize for creating so much confusion and have noted the above posts to redirect here - I leave my original comments for the record.
Here are the Official Ubuntu Flavors that agreed to abide by Ubuntu dropping Flatpak:
- Ubuntu Mate
- Ubuntu Unity
- Ubuntu Studio
- Ubuntu Kylin
- Ubuntu Budgie
- Lubuntu
- Kubuntu
This solves the mystery of why the flavors would agree- as they are Ubuntu. Not Distro Derivatives that use Ubuntu as a base.
This also highly suggests that Zorin OS, Mint, Pop and other distro derivatives are uninvolved with this fiasco.
It's still worth discussion, though.