N,
Typically, in a training class, when you're THINKING about the process as you go along, and your attention's more likely to be on what you're doing than what the target's doing, it's not as critical.
As a former firearms instructor, and one exposed to Ayoob, Farnum, Tueller, and Taylor, along with a number of years in uniform, I can categorically state that once the stress of handling a "target" that may be trying to kill you with knife, club, or gun hits, your attention will not be on the draw & presentation process. Much goes to spit under those circumstances.
Yes, training and ingrained motor responses will carry through where conscious thought does not, but, those are large muscle movements, and fine motor skills deteriorate rapidly.
In a high stress encounter, your brain will be attempting to process incoming information streams, and tachy/psyche effects will kick in. You will not be concentrating on making sure that little safety really did get wiped off as your thumb went on by. You will not put conscious thought into making sure you put enough pressure on it to positively disengage. The pattern will most likely be there (with no guarantee even then), and the relatively large-muscle-movement of swiping your thumb down over the lever will most likely happen, but with the size of that safety lever, it's very easy to just slip right on over it without deactivating it completely. (Ruger, incidentally, warns in the manual about not leaving the safety half on or half off. They may have some concerns about that lever to cause the caution to be there.)
The part of your brain that controls the thumb response will most likely (there are no absolutes) do its job, but the conscious part that emphasizes making sure the lever actually went down at the range, won't engage in a hyper-active threatening situation.
This has even been known to happen with 1911 users, in forgetting (lack of repetitious practice) to hit the safety, or in not engaging a smaller lever completely, under stress.
We teach certain principles (secure but accessible holster, simple to bring into action handgun, visible sights, usable trigger pull, etc.), and borrowing from the 1911 platform, one that I find important is that a defensive pistol should have certain attributes, among which are prominent & easily accessible controls.
The SR9's not a bad pistol, it can just be a better pistol.
Not, incidentally, the only pistol in the world I say that about in factory form.
If the stock safety works for you, great!
Denis
