In your opinion it may not be "advisable" but the information on getting it pre-academy/rotc/ots is out there and even posted on official websites. IMO its an option, especially if you don't want to be limited career wise by vision requirements, maybe I'm thinking too far ahead.
Again, you are just wrong. It's not that it is advisable or not (which it's not at that age anyway for the most part) PRK or LASIK to get within diopteric power limits IS NOT a way to get around the waiver requirements. Maybe I'm reading your statements wrong, but here is an example for illustrative purposes:
18 year old person wants to join the Service. Their spectacle correction is (insert random high number...) let's say -9.50 Sph. (The Sph part means they have no astigmatism, but just as easily they could have some as PRK/LASIK will correct that too).
Okay, obviously they are beyond the limits of what the Services allow for commissioning. For illustrative purposes, let's use the Navy requirements (no matter the commissioning source) which is +/- 8.00 Diopters to obtain a commission and +/-6.00 Diopters for starting a program "which leads to a commission" ie USNA/ROTC. (which can be found in MANMED Chapter 15)
They go ahead and go get their refractive surgery of choice and now whala (how do you even spell that, wala? whaalllaaa?
) they have no need for glasses AND their new refractive error is Plano Sphere, meaning they have 0.00 Diopters of refractive error.
Guess, what....they are still DQ! They still require the EXACT SAME waiver they required before they had refractive surgery. They have done nothing to improve their chances at getting a waiver, and in fact have introduced another potential problem in their history by having PRK/LASIK completed at an age when most would say the eyes aren't quite completely developed. AND they've introduced risk to their vision that wasn't necessary in the first place to get to their end result.
Ah, but you say now they've opened the door to being a pilot once they get their commissioning waiver. Well, guess what, that's not quite true either. The requirement for Student Naval Aviator vision is -1.50 to +3.00 Diopters. Well, they meet that requirement, because right now they are 0.00 BUT the requirements for someone that has a history of PRK/LASIK is that their PREOPERATIVE power be within the +3.00 to -8.00 range. So, they are disqualified from that as well and once again, getting PRK/LASIK prior to entering the service gave them no advantage or help. Now reality is they are 3+ years out from their original surgery and since they had surgery at a younger age they likely have had some myopic progression and in reality their prescription has progressed to -1.75 and now they are again outside the limits for pilot again. So now they go back and they need a second surgery, but since they had one already they don't have enough corneal thickness left to safely perform the surgery so now they are completely out of luck for being a pilot.
Your example of the Air Force Academy from their website is interpreted incorrectly. They are not suggesting that someone who was a -9 correction and does not get PRK/LASIK would not be granted a waiver. They are simply stating that someone who is between 8 and 10 has a chance for a waiver and those beyond 10 are unlikely to get a waiver. The placement of that statement under the discussion of PRK/LASIK does make it slightly ambiguous to someone who is not intimately familiar with these standards.
I may be coming off harsh here, but it's because I really don't want a young person to come and read this thread and think they've found a way around needing a waiver for their near sightedness.