I agree with the others who have written that the marathon isn't Ritz's best event, regardless of what training he does.
Ritz obviously has an incredible "engine." However, the problem in all his marathons hasn't been the engine, it's been cramping in his legs or other "mechanical" stuff. I think it's likely that he's a) too fragile to handle the pounding and b) too fragile to handle the density of mileage that would allow him to handle the pounding better.
For a guy like Ritz, 4:50 pace has gotta feel like he's walking. On the other hand, the marathon is over two hours of pounding, and it doesn't seem like that's Ritz's bag. Compare that to a guy like Brian Sell, whose half-marathon PR wasn't much faster than 4:50/mile, (correct me if I'm wrong, but he ran like 1:03:00, I believe, but again, I'm not 100% on that) was a guy who could handle the density of training very well, and could run hard for 2 hrs + without damaging himself nearly as much as Ritz apparently does.
Now I don't mean that as some chip-on-my-shoulder "Ritz is spoiled and Sell is just TOUGH blah blah blah" bull you hear spewed about here and there, I'm just commented on two very good runners' relative strengths.
Regarding Salazar's marathon training, I think Josh Rohatinsky's comments regarding Salazar and "training fads" were very revealing. Basically, Rohat claimed that when Salazar had a good idea, it wasn't enough to implement the idea, you had to take the idea and apply it to the nth degree. The trait of refusing to be complacent in one's training program is a good one for a coach, I think, but like all things, it can be used in excess. I'm not a big fan of how much Salazar talks up his athletes, either, but at the same time, like it or not, there is a marketing approach to our sport, and even if you tune in to a race hoping the Nike athletes fail, you're still tuning in.
Lastly, Salazar's idea to build speed first and then condition for the marathon is nothing new. It's how he trained for his marathons when he was crushing 2:08s and 2:09s back in the 80s, and more recently, it's a very successful methodology used by Canova, Gigliotti, and Claudio B. To claim marathon training CANNOT be what Canova et al do is to deny the dozens of 2:06-2:08 runners they've produced.