Perhaps it's technically incorrect to use the term "control" when the piece is occupying the square itself. I understand what the author is saying of course and do not disagree about the strength of the move Nde4, either. Althought there is not just one knight standing on e4, the knight on c3 and pawn on f3 are effectively supporting the occupant on e4.
A potentially better explanation might go: "White ensconces his knight into a powerful central blockading square, discouraging aggressive moves such as Nc5 or Ng5 by black. "
In addition, I've discussed various pawn structure books which may be of interest to you a blog of mine https://www.chess.com/blog/2Bf41-0/important-pawn-structures
Please let me know your thoughts, 
2Bf41-0
White to move and moves to Nde4. The analysis from the book "Chess Structures; A Grandmaster's Guide" declares that after said move white controls the e4-square.
But here is my lack of understanding of square-control: white is standing on it, so how does that make it "in control" of it? I always though "control of a square" means having pieces aiming at it, not occupying it.