Has this been resolved somehow, perhaps with some feature to manually refresh last-updated timestamps to ignore deleted posts? Sorry to necro this old thread, but Search couldn’t find a more recent or relevant one.
Today we had to block+suspend a user and delete their >50 spam posts (and reset our Rate Limits which allowed that to happen, whoops!), but the ancient threads they necro-spammed are still showing up with recent timestamps and listed in our Latest Topics accordingly.