I buy that, but I also think that the reason it's not understood is that no one really cared to study it because it's illegal. It doesn't really take a whole lot to set up a performance experiment similar to the one that supposedly arrived at 0.08 BAC is the line where one has a significant performance effect on driving, and if more states start falling in line with CO and WA (and I think they eventually will), the military will have to figure something out.
THAT was more my point. The military will never let it be legal, but why?? If not for flyers, then what about office rats? They don't have a critical need to be at 100% the day after indulgence (just like I'm sure many of them show up to work with a hangover and never get caught). So, is it just a matter of intoxication period? You can be high for a couple hours, and be drunk for 12+ hours, depending on how much you use/potency. Is it a matter of not being able to screen people (ie: breathalyzer for a "fit for duty" check?) At least that's a valid argument.
However, there is a disconnect between what "Big Navy" claims the policy is and the general sentiment of the Navy in practice. Whatever, the real reasoning, I've personally sat on an ADSEP board in which drugs were a factor and I was outvoted by people for a lesser discharge due to their personal moral ideologies. "Drugs are BAD, so he deserves OTH. Fuck him". So whatever is the reasoning from the top, in practice, the Navy's execution isn't just a matter of how drugs intoxicate you. It is a very grey area filled with morality and other such nonsense. No one seems to understand how drugs were made illegal in the first place in this country....