Calling it a 3-5-2 rather than a 5-3-2 is a good start to trying to portray it as offensive and fun.
I agree though, it is quite telling when LVG considers United less capable of playing a 4-3-3 than Holland who didn't revert to a 5-3-2 until an injury on Strootman.
A 5-3-2 is different from a 4-3-3 in two ways. You add another defender and you make your wide players more defensive. Two completely defensive tactical changes.
We will have issues when we are up against teams who happily sit back and let us dominate the game. Moyes and Mourinho found out last year just how many points you drop if you are specialized at counter-attacking as a top club.
I have nothing against a 5-3-2 in bigger matches, but we will need something different in 90% of the season we are heavy favorites going in to the matches.
Then we'd probably need to actually play an offensive 3-5-2 with three central defenders and two wingers out wide, or at least one offensive winger. That is Januzaj/Nani rather than Young/Valencia.