Age can go both ways as well - some gyms only want kids below a certain age to be on pre-team, but they would also need the child to be old enough for the class to be age-appropriate. E.g. I had a 4-year-old in a pre-K class once who had a lot of the skills needed for pre-team or even level 3. I'm not kidding...it's like something off of CGM YouTube, but she could do a pull-over, back hip circle, good cartwheels, and a backbend kickover completely by herself (I didn't do bridges with kids that young, but she came into the class already knowing it and wanted to show me), and a passable handstand, and had pretty good form. But there was no way we were going to move her into the pre-pre-team because she was just too young for that class to make sense. She stayed in the least popular time slot for my class so that she could get a lot of individualized attention that would also be age-appropriate.
I feel like you're practically talking about my kiddo. Although, she's only 2.5. She's not as advanced as you mentioned, but I wouldn't be shocked if she is by that age. She goes to class 3x a week. 2 mom and me and 1 private. The groups are for her sensory needs. She has a lot less sensory seeking and maladaptive behaviors on gym days to begin with. The privates were originally to work on her listening skills in a sensory-rich environment.
What she's lacking through developmental delays (speech delay, speech processing delays and sensory seeking issues, along with severe aggression and social skill issues), she completely makes up for in her athletic abilities.
She was practically born with a 6 pack. Had a 10 second flexed arm hang at 6 months, now around 30 seconds before she starts goofing off. She has had underweight issues since birth, yet gained 4 lbs. in a month of starting gym, and it's all muscle. She also is ridiculously flexible and has great balance for her age.
Within the first month of her just being in toy class she had one of the (what I'm assuming from what observed) elite level coaches comment on how he's noticed her and her strength/abilities. He even joked about elite tracking her now. Her private coached has already started talking about putting her into the special conditioning class a year early (3.5 vs. 4.5) because she's already at around a 4-5 strength level. And they're not just some overly excited coaches. They're a well established high achieving school, with multiple Olympian alumni.
Basically though, my point of responding to this comment in particular is to point out that not all CGM's are purposely CGM's. I want to avoid becoming one at all costs (I taught Tae Kwon Do for years, and boy, if you think gymnastics attracted the crazies...). Ur there's absolutely no denying my kid has unnatural abilities, every coach that even just sees her comments on her and most of the other parents. Now how far she'll go? That depends on her.
Also, if you've ever seen the old TLC special on the strongest toddler ever (or something like that, his name is Liam Hoekstra), that's basically my kid, but I can verify it. My sister even joked about it within minutes of her being born because she was so muscular. Whether she has a myostatin deficiency though, we do not know yet.