Signal clients have a built in time bomb in each version to "force" you to upgrade after a period of time. It can, of course, be patched out (and I patch it out, along with other fuckery such as disappearing messages/expiring messages/remote delete) but to say that "reproducible builds + content-addressing distribution" solves this problem is basically false in practice.

Also, on iOS, almost everyone has app autoupdates turned on because that's the default.