You're attributing a gymnast's ability primarily to their being smaller? Really? It takes incredible strength and balance, among other things to do what they do. If your standard of "athleticism" is one athlete being able to do what other expert athletes do, then guess what: MOST elite athletes aren't athletes!
Do you think Lebron James could consistently hit a major league fastball in his prime? And your example using MJ actually DISPROVES your point. He sucked at baseball. The fact he could even be sorta less sucky is because of his raw athleticism. How many football, basketball, baseball players, or Olympic sprinters or skiers could do a rings routine or the pummel horse routine? Your own theory proves my point. If gymnasts aren't athletes because they can't translate to other sports, neither are the ones I just mentioned.
You're adopting an extremely unfair and narrow definition of athlete that is frankly comical.