Redshirting
I talked to a DI coach this year and asked how his boy was doing knowing he was close to being a freshman. He said he was a freshman and was very undersized for the weight. I asked about redshirting him and he said they presented the option to him and he wanted to stay in the current grade. It was interesting hearing that from a DI coach.
On the other hand another DI coach's son took the year off to "find himself" or whatever, aka redshirt.
The point is that until the IHSAA changes something people will continue to do it because they feel it will help them. I'm personally not a fan of holding a kid back for athletic reasons, but there really isn't much that can be done at the current time.
Transferring
While no one enjoys seeing good kids go to the same school it is more and more common. Go back the last 10-15 years and find me state champion teams that didn't have at least one if not a few kids that were originally out of district. There are reasons kids want to go to these schools. They train with each other during the off-season and form friendships off the mat and want to continue to train together. They also train under those coaches and want to continue doing so, especially when their home school coaches aren't around in the off-season.
One other thing to realize is most of these schools are closed districts so most of these families are moving their WHOLE family into the district and likely purchasing a new home there. That is an extreme commitment to this whole transfer scenario.
Whether you like it or not, people will continue to give their kids great opportunities to succeed. I know personally we moved 8 years ago for our kids and the school district was VERY important to us. In five years if my son is good at something and another school is a better fit I know we will look into the possibility of him going to another school. In the end as a parent you always look out for what is best for your kid and want to put them in places where they will thrive.