Ummm, nope, I was saying it’s twice the power (thus heat), because the MT-G2 and XHP-xx are “6V” chips, not “3V” chips.
So whether you’re supplying 3A from 2 cells in series, or 3A from 1 cell and boost driver, you’ll be burning off twice the heat vs 3A to a single-chip LED like an XM-L.