Snap has absolutely no system libraries and handles them by bundling them per package. Flatpak does kinda the same thing but a few core ones get bundled in the runtime. As far as I’m aware you can’t update libraries without rebuilding the snap completely. There are a lot of things you could say about this behavior but “sane” would not be high on that list. Stable maybe. I’ve had flatpaks break because a bug got introduced in a runtime. Snaps probably wouldn’t have that problem. But those underlying library updates are shared. You update the nvidia-opengl runtime once and it updates for steam, heroic and all your emulators. Meanwhile unless I’m fundamentally misunderstanding snaps, when a new mesa feature is released, you need to wait for the snap maintainer to update the snap before you can take advantage.