Think he's confusing "style of play" with "attitude & application" when referring to DNA.
Fergie never had one style of play he applied throughout his career. What he consistantly did was he installed a sense of belief that the players always could win so long as they applied themselves, no matter how shit they were playing or if the tactics weren't quite right.
If Rangnick is going to come in, he needs to install that ideology again, as well as an overall different approach to tactics. Bringing back that big club mentality and fear is one of the biggest challenges, but is in essence the "United DNA".
To make sure at least part of my post is relevant to the thread, love Evra as a character and what he did for the club, but a complete loony and has no idea what he's talking about the majority of the time as a pundit.