Second balls aren't in the air though. Sure, winning the header on midfield helps, but winning the Second ball is even more important. Which is why targeting a short CM slash DM with long balls is a bot insane.
It might guarantee you win more headers, but it doesn't guarantee you more possession if we win the 3nd ball. Something we work hard on winning regardless of who wins the actual header.
Don't get me wrong, having Bogbrush, Matic and Pogba will give you an ariel advantage on lumped balls against Kante, Vidal and Fernandihno. But in the middle of the park, I'd bet Vidal, Kante and Dihno win more of the 2bd balls. Simply because they are harder workers.
The height advantage becomes an issue on set pieces. When you have to match heights. Generally you just match your talk guys with theirs. Sure we are a shorter team with Stones being the only tall ladder. And this is a legitimate issue. BTW another advantage of Maguire.
But in central midfield it really isn't that serious of an issue. Now if you have talent of equal quality sure being taller is a plus. But if the shorter player is the better player, you take him every time.