You’re strawmanning their comment— I’d imagine they’d have the same, if not more, issues with snap.

Flatpak doesn’t integrate well with all systems. For me personally, on Arch, I have to update and store Flatpak versions of some dependencies, like proprietary Nvidia drivers, separately from the rest of my system and its package management system. And it does take up some space to store the runtime too.

Also Flatpaks may require some extra set up and/or workarounds due to their sandboxed environment. That’s not inherently bad and has some big security upsides, but it’s a consideration.

Also I don’t know how well it plays with immutable distros, but I’d imagine there may be similar integration issues there, too.

It’s still probably a lot easier for devs to have a consistent distribution format though, and they are typically more secure, so I’m not saying there’s not merits to only providing a Flatpak. Just pointing out that your reply here was misguided, imo.