I think the difference there is that Khamzat has the wrestling to dictate exactly where the fight goes and the pace as well, while Zabit was leaned more towards his striking rather than an overwhelming wrestling game. Not to say he wasn't adept there as well, but he wasn't as good or suffocating with it compared to Chimaev.
The other thing is that Khamzat only looked vulnerable against a title contender (Burns) who was a bad matchup for him due to his BJJ, and a former champ with impeccable takedown defense. Compare that to Zabit slowing down vs Stephens, Kattar and worst of all, Bochniak.
I think he'd have capped out as a top 3 guy if only because the two best fighters he'd have to get past that at the time, Volk and Max, are incredible in 5 rounders and don't concede ground very easily.