We are former a homeschooler/current online-school family and I am just saying from the start that we did not homeschool because of gymnastics (though it did make things easier). My daughter was never anywhere near the elite track so I have not bias there.
I get that there is concern about ensuring a "good" education but that can take many forms and alternate routes are not necessarily inferior, even when they may appear that way. So a family puts schooling on the "backburner" for a few years and the child falls a little behind while pursuing his/her dreams. That doesn't mean they have now ruined their child's life. If/when the child wants to go to college, they may have to spend extra time catching up but in the grand scheme of life, so what? Our traditional schooling has us programmed to believe that we must follow that PreK-12 and immediately onto college path and that students need 6+ hours of schooling a day, but that simply isn't true. Until you get to high school, the only subjects that really matter are reading, writing, and math. On average, that takes no more than 3 hours a day and add an hour of independent reading/learning for history/science through middle school.
If a gymnast is looking to compete in college and is on the elite path, they are in contact with the coaches and admins by 6-8th to make sure they are taking the steps to be academically eligible. Yes, there are girls who fall through the cracks and find themselves missing credits but it doesn't happen often and most are able to correct this.