He can do better TTs than this. He will be better in the flat TT in the first week of the Tour. He already said that he needs to be in peak shape to do great time trials, it's not just because of the specific factors in the 3rd week. When he is not in peak shape, his abilities on TT resent more than in the mountains.
Despite that, he does decent TT outside of the Tour, for a guy who weighs less than quintana.
In normal conditions he is not so good like he is in the last week of the Tour, but also he is not that " bad"like TT the perfomances he showed lately. The TT in Copenhagen in worst conditions than his opponents, shows that.
Of course nobody expect that he will take time on his opponents in the first flat TT of the Tour, but he will not lose much time if he goes in peak shape.