Sometimes I’ll like a thread but never bother to interact with it, so maybe it’s like that?
From how I’ve always understood the “at least” and “likely higher” stuff, it’s for characters who are much stronger than a certain tier and could potentially be a higher one, only there’s no exact tier to place them in (that seems to be how
the Attack Potency page describes it as well). With the Low 1-C Ninjago characters, saying they’re at least Low 1-C implies that they’re so far above the 5-D part of the cosmology that they could potentially be 6-D or higher, but they don’t seem to have anything like that from what I could see on the profiles.
As for Dragon Overlord > Spirit Overlord, idk. Currently the Wiki considers SO to have Unknown stats outside of Low 1-C durability, which seems more due to his state of being rather than anything else. I’m not sure if DO would be that much stronger than SO’s durability or not. Even if he was though I don’t think the difference would be a tier’s worth.