So having a look at dream stuff and other CRT's / threads, and it seems like we currently treat any dream in the series as automatically being universal based primarily on Future Dream in MP5 and Subcon stuff from SMB2 and BS SMB2?
BS SMB2 does say there's
as many Subcons as there are peoples dreams which would indicate that much like the main Subcon in the game they're all universe sized, but that was nearly 30 years ago and more recent games like Dream Team do seem to contradict the idea of every dream world being that big with the example I gave of one of the dream worlds needing to be expanded to make room for another island since before then it was deemed too small to hide Peach from Bowser and Antasma.
Granted even if we decide none of the dreams on Pi'illo island are universal we
might still have tier 2 ratings, the Zeekeeper crossing dimensions in it's boss battle is actually him creating dimensions in the original JP dialouge and that should be applicable to his AP since dreambert says the creation of dimensions is the type of power they need against the dream stone and the Zeekeeper's method of destroying the barrier made by it is with a energy beam. Although it does depend on if we wanna consider the dimensions he makes as universal in size too.