Aldo is a much better fighter than Sterling. Yan obviously knew that as well, he did train with Aldo in Brazil back in 2016 I believe, and always respected his skillset, especially his boxing and his kicks. Sterling's grappling, just like I said before is low level compared to the Dagestani wrestlers that Yan is training with. Sterling's striking is pitter-patter punches and Yan is a tough dude with a great chin.
Stylistically Aldo is a much tougher matchup and Sandhagen is also stylistically a tougher matchup for Yan than Sterling was.
Just sucks that we have to deal with this fake clown champ Aljamain until Yan tools with him in the rematch.