Mobile platforms like android and iOS (more specifically GrapheneOS), are leagues ahead of desktop operating systems in terms of security because of these strict policies. and besides, you are treating untrusted code as untrusted code. I don’t see the flaw in that logic.
sure, they could use more apis for accessing system directories and stuff like that securely, but that’s not really in scope. this is for end users. not field deployment on an sbc for something.