I think it's a difficult one.
Personally, I don't think I would be prepared to sacrifice my dd's childhood for something like this. I feel it's too intense, too much pressure, too soon. However, my dd has no particular sporting talent so the question has never really arisen.
My friend did face this kind of dilemma when her oldest dd was at primary school, but with gymnastics rather than swimming. She signed up to a very intense and gruelling training schedule, with similarly strict rules about holidays, time off etc. Weekends seemed to revolve around competitions and the like. The girl in question is now 17 and she does compete internationally with a fair amount of success, but she is not quite good enough to reach the very top ranks of the elite. Would she say now that it has all been worth it? Would her answer have been different if she had now been preparing for the Tokyo Olympics? I honestly don't know. However, I believe her younger sister has paid a significant price for her sister's success, as she has spent much of her childhood trailing around from one competition to the next. I wonder if she would feel that it was all worth it.
Sadly, I think the reality is that most people who go on to do sport at an elite level do make enormous sacrifices as young children, and so do their families. However, for every one who actually makes it, there will probably be another 100 or more who don't. And when you sign up for that level of commitment, you don't know how it's all going to turn out.
I guess the only sensible option is to assume that your child is not going to be among the very few who make it to the very top, and then decide whether you'd still want to sign up to that kind of training schedule in any case. Personally, I'd be encouraging the dc to enjoy their sport as a hobby but to maintain a balanced life with plenty of other stuff in it, but I'm aware that the parents of elite athletes would probably make very different choices!