I’m not really seeing where there would be a great need to “show all of them”.
I set my preferences to “new when haven’t read them” and was presented with more than enough. True, the number said 500 and after reading a bunch the next time it again said 500. So I suppose it could be a bit confusing to those that don’t understand what’s going on. But it isn’t like I read anywhere near 500 all in one go let alone if there had been all of them.
Maybe simply having a plus 500+ would be good enough?