No.
But say, I’m currently looking at my Subscriptions sorted by New. I doomscroll until I see stuff that is 10 hours old. While I do that posts could come in that are 5 hours old. But the next time I doomscroll I wouldn’t go that far back because I think I’ve already seen stuff that old.
If what I have seen already was automatically marked as read and not showing for me, I would still see the 5 hours old stuff because that wouldn’t have been marked as read.
I should dust off my Pinephone.