A lot of changes get made that aren't "do or die." NFHS would have been just fine without the 40-second clock. But the research from the higher levels and the experimental states concludes that most believe it makes the game better. I see no reason to keep it away from the high school game. Your constant patronizing reminders about whom NFHS rules are written for are not really relevant to why there should or shouldn't be a 40-second clock. The game evolves. Either we evolve with it or we get out.
Unfortunate, that you consider reminders about relevant differences between the DRAMATICALLY different (Maturity & Physical Capability) levels of participants at the various levels of Football, as patronizing, but the reality is, they are significantly different. Improving the game, as well as the safety of the participants, is absolutely a laudable objective. However, "Improvement" much like "Beauty" is very often, "in the eye of the beholder".
Much can be learned from higher levels of execution, but each of those levels hold much higher value in specific, valid objectives, that may not be as relevant, or necessary, to what amounts to the "basic (learning) level of a very complex, demanding and rewarding game. Evolving differences in the overall game of Football, designed specifically to address circumstances and objectives to benefit higher levels, DO NOT AUTOMATICALLY translate as well, or as necessary, to the Interscholastic level. (Which is why so many subtle differences currently exist)
As suggested, "TIME WILL TELL" whether the 40 second clock, and all the associated necessities and requirements to transport this capability will benefit, and/or improve Interscholastic level football.
The game does evolve, the choices you suggest ("evolve with it or we get out") should also include a 3rd option of carefully deciding, and assessing, if adopting a solution from higher play levels is BETTER for the needs of the Interscholastic level, and whether the overall changes necessary to support the plan are worth the anticipated benefit rather than simply mimicking what, may address well, objectives and necessities far more unique to progressively higher levels.