I don't think it's a matter of how fast you can progress but flexibility in progression instead of this "one size fits all" approach. Fastest possible progression isn't always the best approach and I have the PM's to prove it
There is a difference between recieving instuction on the lifts and "learning" them, for one thing. Taking a new exercise and aggressively loading it right off the bat, workout to workout, isn't always going to be best for the long term. What I see is people starting out great simply because the weights are light and then 40 to 50 pounds later their squats look like a big pile of meat with a barbell on top of it. And they are back tracking and trying to figure out what went wrong.
SS is a good starting template, I think, from which to proceed but it suffers from over-rigidity and a too enthusiastic belief in it's own infallibility. There are some simple and beneficial things in terms of useful variety that could help people keep everything moving in a healthy way and also take care of the strength gains AND the mass gains without being totally obliterated by the SAME thing all the time.
Simple is good but the problems is RULES instead of GUIDELINES.
I used to recommend it across the board but I found myself in the journals writing thesis's on fix-ups for what is supposed to be simple and straight forward all the while thinking it could have been avoided by some simple modifications. There is a lot of stuck in the mud thinking in it.
What defines a beginner is that he can progress more often and yes, more than once a week. But that does not mean he needs to dig a hole in the floor and basically dial in all the imperfections he picks up from a too-agressive and unbalanced approach.
People suffer, as I've said again and again, from trying to decide between extremes. We look at bodybuilding splits and we see a bunch of useless variey for the sake of variety so we say...you only need to do this handful of thing day in and day out. One exteme to the other. So you end up with bodybuildinder's doing too much variety with no clear purpose and "strength and mass" people doing not enough variety if none at all.
Sentinel put in ghr's, for instance, because he knows that getting those glutes (and hams) on board is going to do a lot to power people's squatting and keep them healthy in the long run.
My solution would have been to simple replace squats with a wide stance single leg version to do the same thing with a compound movement that works the whole hip and leg but blasts the glutes and hams, helps with typical imbalances, and improves squatting in the long run. Plus it give you big ass legs.
3x5 and 5x5, when it comes down to it is middle ground strength and "bodybuilding" stuff. So it's kind of funny that it should become so stifled in other ways too and become completely middle of the road.