In general, you should not comment on an article you haven't read. However, going off the extracts I think Cox has put 2 and 2 together and got 5.
Is it true that Ole's coaching ability shines through most when he sets up to be compact and counter? Yes.
Is it true that a lot of Fergie's old players have not proven to be attacking coaches? Yes.
Is it true that Fergie never had an attacking style of play and got all his ideas from outside?
No.
The quoted bits of the article make it seem like Cox is basically saying: Cos none of Fergie's players could do what Fergie did then the idea of Fergie's style is a myth. This seems a strange bar to set. That's like saying that Ronald Koeman's boring football is evidence that Cruyff's style never existed.
Fergie was very much a great coach with a pleasing style of football to watch. He introduced several tactical innovations and plans to the English game e.g. playing with no target man at Carrow Road in 1993. Developing specialised marking plans for Steve McManaman. Where he brought in coaches from outside it was to help him execute his own ideas e.g. Fergie had tried moving away from 442 in Europe before Quieroz was appointed, with Veron. Quieroz didn't give Fergie the idea. Fergie saw in Quieroz a partner that would help him realise his own vision for how to modernise his team.
Its like people listen to the likes of Van Persie and Rio talk about how Fergie directed the midfielders to look for Robin's runs and ignore it, because the media says Fergie didn't do any coaching in his later years.
The man had clear ideas about the game, he worked on what he wanted to see when his team had the ball and he was able to execute that vision over decades to win trophy after trophy. I dunno why its become fashionable to treat Fergie like he a Scottish Kevin Keegan, pumping up his teams on emotion. Very strange.