He has won 3 of the 5 ITTs he has contested in the first half of a Grand Tour, finished second by the tiniest of margins in one other and crashed in the last.
He has won both ITTs he has contested situated in the middle part of the race.
I think that could be a bit misleading. Firstly, because he wasn't riding for GC in most of them, and secondly because the first week or first half of those races was nowhere near as hard as the first week of this Vuelta has been. He may well still crush it, but he has shown that fatigue affects his performances, way more than it does with the likes of Froome or Thomas, so it's not an absolute given that he takes 2+ minutes.
He's basically done 4 TTs since riding for GC at Grand Tours. The two that came at the end of the race were way below his usual standards. The other two at the Giro were the first stage, and after a week of pretty easy stages.
So I think there is still a question mark there about how much his performance drops off with GT fatigue. Of course, he'll still beat the other three contenders, but perhaps not by some much that it ends the race as a contest.