In county won't really solve what they are trying to solve which is unfair competition. Unfair competition is all-star teams. The rule will at least keep it to county all-star teams, which is a step in the right direction as you pointed out. I guess it's better than nothing and will at least put a limit on the worst offenders.
Since you mentioned Broward let me tell you about my experience today. Ft Lauderdale, Hialeah Miami-Lakes and South Miami were playing a spring jamboree Thursday at 3:30pm. Gofan was selling tickets and listed the game location at Hialeah Miami-Lakes with the address of the school. I drove down from Boca Raton to the school but no jamboree . I ask AI where do they play their home games which is Ted Hendricks Stadium. i drive to Ted Hendricks but no jamboree. I decided to drive to Ft Lauderdale High since it was somewhat on the way. Still no jamboree. I asked AI where does Ft Lauderdale play their home games. They play at Lockhart Stadium. It didn’t make sense to drive there at this point, so I drove home.
And yes, I had already purchased a ticket.
Many teams in Broward don't have spring games because of that rule a lot of years. St. Thomas, Dillard, Deerfield, Monarch etc. It obviously changes some years as to who is getting the transfers.
Also, many of the lower teams have stopped having spring games because their kids get transfer if they lose the spring game or don't get enough stats. Kids don't really understand the purpose of a spring game.
Broward warns the coaches not to play the kids, but some teams sneak them in anyway. Hard to keep track of with so many transfers and 40 schools in a county. I believe the rule is more to keep kids at their school through the end of the school year though. Some will wait until summer if they know they can't play in it and the hope is the original school can do enough to keep them.