Why were the HS rules changed? Does this scheme somehow increase the risk of injury to players?
I could write several paragraphs on this, but I'll just give a brief overview!
The A11 offense originally took advantage of a loophole in the rules that said if in punt or field goal formation (Scrimmage kick formation), the numbering requirements (ineligible linemen wearing 50-79) went away. The intent of that rule was to allow players who normally play other positions to serve as blockers on punts and filed goals.
The A11 pioneers just had their QB stand more than 7-10 yards deep in shotgun formation, so, technically, he was in "scrimmage kick formation" -- this allowed the linemen to wear any number. There was no intent to punt. The QB could then legally pass the ball to any player, so long as they were eligible by position (ie, on the end of the line or in the backfield.) So, if your left guard wore #88 and took a step back into the backfield more than 1 second before the snap, he could go downfield and catch a pass. Anyone could catch a pass so long as they were eligible by position.
The rule was changed a couple years later, my understanding is for 2 reasons:
1. It was never the intent of the powers that be to have this happen -- the rule was for the purpose of punts & field goals only.
2. It was extremely hard to officiate. The covering officials would have to essentially memorize the position of all 11 players just 1-2 seconds prior to the snap . . .essentially, that's impossible to do.
(I've officiated high school FB and would agree with point 2, though I never ran into this formation ran on purpose!)