Hmmm.... then why did Caro say "It was like someone turned the sound off" when he switched to holdem?
I don't know, I haven't a clue what he's trying to say!
As for the most skill, you could define this by the game at which a good player is most likely to beat a bad player. I don't know what the answer is. It's complicated by the fact that Omaha, for example, naturally shows higher variance than Hold'em. So over the course of one game, you could say that Hold'em requires more skill than Omaha, because the more skilful player is more likely to win.
But over the long term, it may be that Omaha or some other game will produce a higher average win rate for the better player. Omaha certainly has more luck involved, but that doesn't mean there's less skill.
And this comes to why it's difficult to compare the games - big bet games will produce higher win rates for good players because the bets are bigger. But this doesn't necessarily mean it's more skilful than Limit Hold'em, because Limit would produce equally big win rates if you make the blinds big enough.
I suppose you could measure skill by the amount of time and practice it takes to become a break-even player at stakes appropriate for a given
bankroll. This, however runs into the difficulty that the average player in some games will be more skilful and have more experience than in others, i.e. low-limit hold'em games are harder to beat with 10 hours' experience than low-limit Razz games. But if everyone played Razz all the time this probably wouldn't be true.
So I'm basically saying you're trying to compare apples with oranges... if I had to give an answer I'd say No Limit Hold'em, because everyone else is better at that than other games, so you are required to have more skill to play it.