This fascination about 3-man defence isn't all that bad imho. Every coach has his preferred tactics, what matters is if they know how to make it work. There are very few Capellos or Ancelottis who can work with different systems.
All Mourinho has ever done is play a fast counter attacking 433/4231. He has coached some great players across his clubs which he could have used to play a more possession oriented or different style of football. But that's what he has ever done.
Ferguson has always played with wingers. This season, he had a great attacking midfielder in Kagawa, and Rooney as a no. 10, but he couldn't play any system apart from a 442/433 which even made them play on the wing which aren't their true positions.
Its irrelevant if Mazzari is hellbent on a 3-man defence. What matters is that he has got his teams to play that formation well, which has looked defensively stable and potent in attack.