I am not an expert by any means but I do read up and have tried many many routines and have come to conclude that their seem to be infinite routines out there claiming to be better then the next one. But if you look at the whole picture, all routines (mass/strength routines) equate to one thing, stimulating the muscle and increasing weight . Their are several ways to do this and and in my opinion how you do it is not important, it's the end result that is.
For example look at the HIT routine. You may do 1 set of bench press with the upmost intensity and extremely slow cadence which will result in stimulating the muscle thus causing growth. You can argue HIT is effective because it allows you to fully exhaust the muscle in a very short period of time so your body is still in its prime time and their is no risk of entering a catobolic state. This is a good point but any smart lifter should not be in the gym more then 1h anyhow.
The 5x5 routine is similar to the HIT routine in that the main goal is strength. Increasing strength will undoubtedly result in increased size because the muscle must compensate for increased stress. If strength is increasing then that indicates you are stimulating the muscle. A beginner can increase strength to a great extent without seeing much gains in mass simply because his muscle efficiency is low.
To sum it up, their are many ways one can increase his deadlift by next month, how one does that is unimportant as long as it suits him/her. If the weight is heavy and you are consistantly improving on lifts then you must be doing something right. With increased weight comes mass... simple as that. A HIT,5x5 and numerous other routines could cause identical results if the right objective is completed.
maybe I'll do 4 sets of 8 at medium intensity but the overall volume can ultimately = muscle stimulus
maybe I'll do 1 set of 10, taking 6 seconds per rep and pretending if I don't complete the lift i'll get shot (very high intensity) which can = muscle stimulus.
maybe i'll lift do as many reps possible in 45 sec which can = muscle stimulus
And I could go on and on but you get the point.
I know I failed to mention a **** load of other details like rest and nutrition but I'm tired. I don't know if this post is really that relevant to the original question but I tend to ramble on.