GamePress
Non legendary raids are regional too
Apparently Pnisir, duskull and walrein raids are only available where latios is. Shuppet, granbull and houndoom where latias is.
https://www.reddit.com/r/TheSilphRoad/comments/8a8f83/walrein_pinsir_duskull_raids_are_only_available/
Edit: minor text fixes.