Nothing in theory makes that an issue of flatpaks and snap, just that both rely on different means to interact with the host system that have been woefully slow to implement. If enough protocols are developed a flatpak or snap should be as capable as a native app with the safety benefits for free.
Interesting, didn’t know it was feasible to make the distribution open.
That doesn’t give me much to complain about in theory, but canonical has lost way too much good faith to give people a reason to keep open snap distribution going for free. They should definitely consider hosting an open store just to get people on board again.