Compare Ruben Dias to VVD. Last season Dias was in the bottom 28th percentile among CBs in Europe's big 5 leagues for percentage of aerial duels won, while VVD was in the 94th percentile. That gap amounts to VVD winning an extra 17.5% of his aerial duels, which seems like a lot.
But the impact of that is limited by the relatively low number of aerial duels they face. If Dias had been as dominant as VVD it would have won him 0.58 of an aerial duel per game. Meanwhile if VVD had been as weak as Dias it would have cost him around 0.9 aerial duels per game.
The point being that even if we were to assume Martinez' height will make him weaker in those situations, the negative impact of that isn't seen in every duel he loses but rather the duels he loses that a dominant physical presence wouldn't also lose. And that number is heavily limited by the relatively low number of those situations CBs actually face in a game. So much so that the massive gap in aerial dominance between Dias and VVD last season didn't even amount to a full duel won/lost per game.