Looking at just the fight, at the VERY least it's another universe where Jean gets her power, so Raven completely destroying it is already proof for Low 2-C for their higher tiers. Though in all honestly, it seems to be more so implied to be a higher dimension, especially considering how the actual white hot room is just that. We try to only look at the animations for feats for the characters, but we do still use things said in the analysis, like their height, when measuring their power. Seeing as how the white hot room is a higher dimensional plane in the analysis, I think that's what they were also trying to convey in the fight animation that the white hot room is a place outside of the multiverse, though I might be wrong on this