I'm confused Minnewaska.
After being logged on for a while if I click on new posts I get a bunch of unread threads (meaning threads with at least one unread post since I last logged on.)
If I click on 'quick links' 'today's posts' I get all unread threads from the last 24 hours.
Isn't that how it has always been or am I not understanding your question ?
“Give a man a fire and he's warm for a day, but set fire to him and he's warm for the rest of his life.” Terry Pratchett