Yeah he’s not as comfortable vs them for a few reasons
1. Most one handers can block returns back deep or low which stresses his good but not great serve+1
2. Djokovic hates attacking slices which they use
3. One handers hit with more spin than two handers, it’s just physics, weight of shot and different-looking ball disrupts his rhythm
4. Just in general these players have more skill and guile and are comfortable in the transition game to the net which also disrupts his rhythm
5. One handers can go DTL easier and their shots are less predictable so to speak - Djok’s game is all about incremental advantages in a point, getting a player off balance and knowing where there shot will go - one handers are simply harder to read for him, the body mechanics aren’t as repetitive and predictable.
Of course the one hander is most effective on clay vs Novak and may not have an effect on other surfaces. And the other caveat is that one must be a good player in the first place. Fed and Stan’s BHs alone are not what troubles Novak it’s their entire game, and their serve+FHs are a large part of it. But time and again, if Nole is not in form or not locked in, he can struggle with these one-handers as they differ from his normal machine-like mowing down of generic 2HBH baseline drones across the tour. Especially if it’s his first time playing them in a while.
As his head to heads with Dimitrov and Tsitsipas show though, once he comes to grips with the weaknesses in their game, the one hander doesn’t present unsolvable issues especially off of clay.
Fun stat - since 2005, Djoko has 15 RG losses. 8 to Nadal, one to Melzer (lefty)… and the other SIX are all against one handers - Kohli, Federer, Stan, Cecchinato, Thiem twice, and he also went down 0-2 to both Musetti and Tsitsipas. Tells us something.