I would disagree with this. My memory is strongly of a traditional W formation most of the time - particularly in the late 50's but also through the 60's. One of the funnier aspects of the overall transition from W to 4-2-4 in football in general was the United team sheet that ITV put up at the start of the 68 Final. They carefully arranged the players in a 4-2-4 formation that bore no relation to what we actually did on the pitch (Wikipedia show it as a 4-3-3 which is even more bizarre). Sadler was listed at centreback alongside Foulkes when, as we all know, he actually played at inside right (an attacking midfielder in modern parlance).
Totally agree with the 1968 tactical formation. Wikipedia have got it totally wrong.
Many years ago I interviewed Dennis Viollet and also Ernie Ackerley who said that Busby was very influenced by Brazils 4-2-4 formation in the World Cup and they used to practice it in training. In 1958/59 and 1959/60 Busby often played a 334 as a variation of Brazils formation. Dennis told me that he, Albert Quixall and Bobby Charlton used to almost take turns at dropping deeper to make it a front four rather than a front five. They would then play with either Stiles/Setters/Nicholson or whoever the other midfielders were in a midfield two or three depending upon if they were attacking or defending.
Dennis said Matt was very tactically astute but never got any credit because everyone just thought he played off the cuff. In Charlie Mitten's book, he also commented on Busby's tactical strength particularly with the attacking playersin the team from the late 1940's.
I think the big question that I have never found the answer to is when did we start playing four at the back...seems to be around 1962/1963/1964.
In a report by Wilf McGuinness for the FA in 1967 (which was printed in the March 1967 FA Newsletter), Wilf mentioned that United had been playing a flat back four with Stepney, Dunne, Noble, Foulkes and Stiles with a midfield three of Crerand, Charlton and Best and a forward line of Herd, Law and Aston. David Herd was almost used as a right winger.
As George matured as a player he eventually took over from Herd on the right wing and his goals ratio improved dramatically once he was pushed up front.
The report went on to say that for many games in the 1966/67 season we actually played 4123 formation with Crerand slightly behind Charlton and Best in midfield but predominantly it was just a variation of 433.