^ No, no, don't worry, you're not coming off wrong at all. I hope I'm not, either!
What I'm trying to say is that you're right - that those who stand absolutely by the "you've gotta have the same gun, same holster, same pants on every day" rule are taking it just a little too far (although, truth be told, I not only wear the same kind of pants every day, but also the same kind of shirt and pants - Old Navy el-cheapos FTW!!!
http://www.facebook.com/photo.php?fbid= ... =3&theater" onclick="window.open(this.href);return false; - that's me, the fat Chinese guy in the foreground, the second over from the right, [standing with my feet/legs together at Chris's request] black shirt and blue jeans, at Cerino's "Marksmanship Enhancement Clinic #1, back in February, and here's me again in his "#2 Clinic," two weekends ago, this time, I'm the first over from the right -
http://www.facebook.com/photo.php?fbid= ... =3&theater" onclick="window.open(this.href);return false; - same everything, with the exception of a different ARES Ranger Belt ..... yeah, I'm weird like that

, but being an academic scientist means that I rarely have to dress like an adult!). Like you said, there's no way to insure that *everything* is *always* the same. There is going to be a little variability, day-to-day.
Even for a weirdo like me - someone who dresses the same every day, same kind of shirt, same kind of pants, same everything - I can tell you that yes, it's never quite completely the same, day in, day out, no matter how hard I may try. An older shirt may have shrunken a bit more. A newer shirt's fabric may be just a bit softer and fit a little looser. Getting out of the car, my pants/belt may actually rotate just a little. After some physical activity, maybe my pants dropped just a tad. It's never quite the same (and definitely not at the micron level!

).
But I also think that it's important that newcomers like me realize that there is something to be said for consistency, and that it can help make up for the areas where we may lag behind those who are more experienced or otherwise proficient - to, if you will, "bridge that gap."
Again using myself as an example (looks like we're both the "hope y'all can learn from our mistake!" type

), I know for a fact that me pulling from the OWB Raven,
now - since it is set up to very closely approximate my IWB Pure Kustom - that the only thing that really makes a difference in draw-to-first-hit time is whether or not I need to clear cover clothing (this to include what kind of cover I'm wearing, as well as the technique I use to clear said cover layer
). This is because over the course of the last year, I've diligently practiced my draw, and that includes the guidance and help of some really good instructors, too. But I also confess that earlier on in the timeline, this was not true, that I was better with the gear/setup with which I had practiced most.
I think that as the shooter gains more experience as well as proficiency, those aspects of one's skill can compensate for the differences in gear and setup.
For me, I think that as long as the gear/setup doesn't absolutely conflict with one-another (i.e. shooting a 1911 versus a Beretta 92, with the differences in the engagement of the slide safety; or, for example, shooting with a strong-side OWB on the range and in training, versus wearing a SOB or cross-draw in daily life [and having never trained with it]), it really shouldn't matter too badly, especially when experience and skills are added to the mix.
All this is to say that while I do strongly believe in the need for everyone to train with their carry gun and carry gear, in their usual street clothing, I also realize that there are practical limitations to this, and that, as one's skill level rises, there also becomes increasing flexibility to this, too (nevertheless, optimal performance comes with consistent practice and intimacy - an F1 driver's car is fitted to his every whim).
Furthermore, it should also be taken into account - in maintaining the line of thought of this particular topic, of-course!
- the need for the student to realize his or her limitations in terms of being able to absorb the tremendous amount of material that a course like this will stuff into them, be it over just a few hours or over days. The student should pick gear which will allow him/her to focus on the materials taught: i.e. the gear should not hinder the learning experience.