West Ham boss Sam Allardyce labelled Van Gaal's side "long-ball United" following a 1-1 Premier League draw at Upton Park earlier this month.
That prompted a reaction from the United coach, who produced a dossier to the media claiming Allardyce's assertion was incorrect and that it was West Ham who had a higher percentage of long balls.
However, Monk - whose side host United on Saturday - says the approach shows Van Gaal's versatility.
"I understand what was said, but in this game you have to be adaptable," he said. "You can't have one set way and Man United have done that well.
"They can change their style in games, which they did against West Ham, and it was only in the last five minutes when they used their strength well with [Marouane] Fellaini to get a point out of the game.
"It's a strength to be adaptable but they can produce fantastic football with world class players all over the pitch.
"It takes time as a manager to implement ideas, he's gone in with a new ideas for players to understand but the run they've been on shows what he's doing works.
"They're already taking his things on board and I can only see them going from strength to strength."
