he doesn’t actually win half of his tackles, he is left on the floor with his opponent streaking away with ball
Do you have a source for this? Winning tackles and headers is one thing that can be measured fairly easily, so the statistics are pretty straightforward, and complications only come from how they are presented.
According to how the opta data are presented on fotmob and fbref, last year he made 72 tackles and the team won the ball on 43 (59.7%), and thus far this year he's made 7 and won 6 (85.7%). At Lille the year before joining, he won 31 of 48 (64.6%).
On whoscored they have attempted tackles, then it's broken down into just tackles and dribbled past. This year he's listed as having attempted 11 with 7 tackles, last year attempted 84 with 72, and at Lille it was 55 attempts with 48 tackles. Those tackle numbers square with what the other sites present.
My assumption is that the tackles number is where he won the ball, but lots of tackles a person would normally count as having been won will result in balls going out for a throw in/corner, or a loose ball picked up by the opposition.
So even if we go with the least generous method of "Did the player attempt a tackle, and did their side end up with the ball?" that combines the two above methods, this year he's at 6/11 (54.5%), last year 43/84 (51.1%), and at Lille 31/55 (56.4%). And if you go with players actually getting past him, this year it's 4/11 (36.3%), last year it was 12/84 (14.3%), and at Lille 7/55 (12.7%).
Edited to add: There's a "challenges" section on fbref, which I'm not totally clear on how the numbers differ, but it shows that he's at like 42% in the early part of this year, and was over 70% each of the last couple years.