I was so confused when I was seeing posts 4 years old. “Old” isn’t even supposed to be an option lol.
Tested with other options, seems like TopWeek becomes TopDay, TopMonth becomes TopWeek, TopYear becomes TopMonth, TopAllTime becomes TopYear, and Most comments become TopAllYear. Active, Hot, and New are unaffected.
So for now, you can enjoy seeing the creation of the Fediverse and read posts in reverse with this hidden option.
I’ll see what I can do!