Whats so funny about that? They are both average as fvck in the air but you'd expect a whole lot more from the 6'2 and natural CB Lindelof. Last season at Benfica in a league with a shorter average height he still just won 59% of his aerial duels across the season (69 out of 117).
Not saying you're wrong or Lindelof is good or anything. The thing is Blind rarely played CB nowadays which the amount of duel he needs to do is evidence. The type of players he had to compete should be easier for him than dealing with known physical central forwards.
Then another aspect of aerial duel is that you don't need to win/ dominate to be considered effective. Why? The ones you compete with not necessarily make good use with the duel they win. Just like pressing, it's about applying pressure if you feel you have no chance to win. Portuguese teams as I see not necessarily try to dominate aerially. Times and times again they try to apply pressure and positional play to take initialize when the ball return to the ground. It's different in PL of course
Again I need to repeat I am not absorbing Lindelof of his shortcoming as he made poor header when playing as RB too. Just saying it's too early to draw to conclusion especially you're taking into account a sloppy period of Lindelof as part of the stats
Edit: I used Squawka for these stats, so let's look at Lukaku for another perspective of aerial duel stats. It said he won 1 out of every 2 headed duel in the league. Then you consider CBs have advantage in major of aerial duel due to the fact that the forwards have their back toward goal; Lukaku doesn't look too bad from stats point of view. The reality is that Lukaku lost important duel which can open the play, or his heading effort when competing with his back toward opposition's goal has much to desire for. Of course you want the stats to look good as it shows for most part that it's not your weakness. However pure stats ain't painting the whole picture of players ability as superior as different positions need different metric to assess their performance.