Makes sense - PPAs are very platform specific, plus from a user point of view a bit of a security nightmare (not the Kodi PPA but the idea of adding lots of different PPAs, often poorly named and difficult to keep track of as a user).

I used to get fed up with PPAs when I used Ubuntu - particularly when you to go through a major distro upgrade and you have to go hunting through all of them to see if they support your new distro version. They're just not a good distribution system for most users.

Also the Flatpak will benefit more users across other systems and has the potential to be more secure (particularly given the add ons people download and run in kodi).

Edit: worth noting they have retired the PPA but haven't built out all their equivalent Flatpak versions. An example of the unpaid hard work and hours volunteers put in to maintain open source software.