Well, he is small so people said that he is gonna be a liability in the air. Then Caf said that Baresi was as small but was a beast in the air, and then denied the reality that Lisandro is, as you can expect from a CB of his height, bad in the air.
He attempted 63 aerial duels last season, and won 32, for an aerial duel win rate of 50.7%, which has to be one of the worst in the league (11th percentile). This season he has won 1 out of 4 (albeit the sample is so small that is meaningless).
For comparison, Lindelof whom Caf claims is shit in the air, won 33 out of 53 attempts last season, so a win rate of 62.3%. He attempted nearly as much as Lisandro despite playing far less. And Varane who is great won 42 of 58 (72.5% win rate).