If you're talking about whether a child training highish hours should be free to make their own decisions about what other activities they do then that's a different angle altogether. I don't see that them driving their own gymnastics journey means that they have to have free will to do anything else they want as well - quite the opposite.
I'm afraid in our household I can't let one or more children call the shots in that way. It takes a lot out of the family to support my dd's choice to train gymnastics - it's her passion and I am happy to support that, but she needs to take responsibility for that choice. Being free to do whatever other activities she fancies isn't always an option. I have to think about my other children and whether they are getting a fair shot at doing the activities they want to do, instead of just fitting around her all the time. And I have to think of the cost.
Yes it would be lovely if she could do piano lessons as well, but that would be another chunk of money and another journey and more hours fit around her. I decided no to that and I explained why and she accepted it. Will she regret not learning piano when she's older? - maybe, but there's nothing stopping her taking it up later.
None of us can do everything we want and have everything we want. She is driving her gymnastics journey by choosing to do that when she could quit and play piano, take up athletics and swimming and countless other hobbies. She's not driving it by doing a load of other activities as well just in case she's missing out. She is missing out and accepts it willingly.