It does not. Flatpak uses the full platforms, the native package manager will install the individual libraries that are needed. This is technically a flathub thing and could be implemented more granularly, but I don’t think that is going to happen.

I’ve started getting warnings about deprecated platforms but flathub is very slow to update the packages that use them (even with reports), which is unfortunate too and not something I’ve encountered in my distro repository.

Yes, of course. But afaik the idea of flatpak is, that every program has a list of libraries and versions of them that it wants. So when program X was built with libfoo version 1 and program Y needs libfoo version 2, you basically download the library twice.

When you go through the package manager, you just download the current version that’s in the repository. This can lead to problems when a program expects some functionality that has since been deprecated, but I never actually had issues with that.

Also, a lot of the libraries a flatpak downloads are already installed on the system, just in a different version, I noticed.

I’m on a home computer that I use by myself, mind you. So if something breaks, it’s just my own problem. If I were to use software in production or even just administer the computer of a tech-unsavy relative, I’d likely use flatpaks or similar for stability and security reasons.