"38 of 43 states have cutoffs that will not correspond with the 8/1 cutoff. 7 states have local district choice, so we don't know if this will affect them. But 38/50 is almost 40% will have automatic trapped players - so this shift isn't changing anything but who the trapped players are. There's also redshirted kids - they are growing in number and they won't be playing in their grad year either."
Not sure what you mean by 40%. But since you're using numbers and percentages, to say this shift isn't changing anything is false. It changes the number and % of players that fall into the trapped bucket. How?
For geographies with 8/1 school start, it changes it from 5 months of trapped players to 0 months.
For geographies with 9/1 school start, it changes it from 4 months of trapped players to 1 month.
As you pointed out, majority of states have 9/1 start. So majority of states will go from 4 months worth of trapped players to 1 month (minority from 5 to 0). Taking your 38 of 43 count as fact, and assuming equal distribution of population by state and equal distribution of participation by month (I know this is not true and should never assume, but makes this exercise easier), we go from 34% of players in the trapped bucket with 1/1 cutoff, down to 7% of players with 8/1 cutoff. Pretty significant decrease (~78%). RE: the assumptions part, even if all states had 9/1 school start, 8% would be trapped players with 8/1 cutoff.
(please check my math)