I agree, they are not A level athlete because the filtering process is fucking bullshit and by that I mean non existent...
In football, Basketball and Hockey, you have kids start from middle school with emphasis on physical training, which means you go through years of plyometric training as well as other types of agility and self resistance as well as strength and speed training.
In MMA, people start late in life and that, they don't take the time to truly immerse themselves in physical training methods. Thus they don't get to develop jumping and explosive ability of a person who has practiced plyometric. Not just any person but a person who has already proved themselves to be superior in terms of talent and genetics with years of training.
Also true with boxing, boxers focus on athletic ability and they go through a structured physical regimen to develop their pinnacle of their physical potential as oppose to MMAs...Let me bang bro!
P.S: I used to train in boxing and muay thai, had to drop the latter because getting kicked in the shin was fucking up my ability to do my boxing footwork and plyometrics big time and thus, some combat sports end up making you goddamn disabled if the trainer doesnt understand athletic training and the world of physical culture.
Hence this is why its important to train like Stephen Thompson whos father taught him a kickboxing style that's based on developing proper flexibility and technique as oppose to being some stand up brawler.