In the interest of disclosure, I did ask this question on other forums. Here is one of the answers I got elsewhere:
There is a reason I abandoned pocket carry for primary.
I used to carry Glock 27 in front pocket of cargo shorts (not the cargo pocket). I was pretty happy with it. But once I started investigating how difficult it would be to get the gun out of my pocket in a struggle, I saw how big a losing proposition that would be. Trying to fish your gun out of your pocket mid fight might be less than ideal.....
On the other hand, I do use the pocket to carry the BUG or "auxilliary gun". But I do not have any illusions about getting it out in a brawl. I know that if I go for the pocket pistol mid fight, I had better have the other guy all but unconscous because it will take one of my hands out of the fight for longer than I feel comfortable with...So it is a good news bad news kind of thing. I pretty much dumped the G26/27/33 for the full size guns when I made the decision to roll with the IWB holster and dress around it. So now that is the primary and the J frame is the pocket carried auxilliary gun.
And this did come from a 'big name instructor'.