In one interview Dr Inigo Milan said that during PDBF TT Pog did what he's capable of i.e. average of 6.3 w/kg for an hour, which is consistent with this number (414). Keep in mind that lab tests are close to a sea level.
How does San Milan know that? There is no data at all from the TT never mind PDBF segment. He also was not at the Tour to see 1st hand.