I haven't seen the picture yet but I assure you that Brent Mikesell always goes well below parallel. I haven't ever heard of anyone questioning the depth of his squats.
I seen Brent Mikesell's video and it has clips of some of his biggest squats and some big competition deads (At least one was 800+). Considering he is missing his entire pointer finger on one hand it is crazy he can even hang on to 600. Here is one of his sites http://www.powerlifting.tv/mikesell
Missed you last week for training. Both of us bummed you couldn't make it. Ended up being just the two of us in the gym that week. Missed my big squat too.