I understand. But a quicker restart can't trump game control. I'm probably a bit hyper about this kind of thing today. We had a referee assaulted last night by a high school player, even after his coach had been red carded in an earlier incident. Eleven cautions, two reds. And, in another game, actually involving the same school, a JV2 player yelled insulting language at the referee, from the bench. Before the referee got to the bench, he had somehow disappeared and his shirt number was not on the roster.
I don’t think you need to over think this. For better or worse, NFHS has decided they don’t want kids lying down behind the wall, and made a clear point about it. So just stop them if they do and move on. It may be stupid, but it’s not a big deal as a ref.
"It works in practice, but does it work in theory?" Brass tacks-wise, yes you are spot-on. More ethereally, I guess this is just another of those drafting calamities that lurk for us all, like Scylla and Charybdis.
Just stop the clock. The few times this is match critical AND NFHS doesn't already dictate a stoppage (i.e. the kid being subbed is on the team leading in the last five minutes), you have the authority to stop the clock if you feel that there's undue time wasting. I'd point out in your scenario, though, if it's a corner the attacking team by rule has to be substituting if there are any subs, and if that team is winning the clock is going to stop in the last 5 minutes. If that team is tied or is losing, well, they are only wasting their own time. Outside the last 5 minutes of the second half, how often are those extra 15 seconds really match critical?