Exactly. People like to think in boxes and don't understand there are no perfect players and if there are then everyone wants that player and the chances he'll play for your team are really small anyway. Sure you can sign big strong defenders that can cope with big strikers. But what if they are slow and panic when they are put under pressure in possession you're going to have other problems. But with Maguire and Lindelof in the team you should be aware of that. There are no defenders that check all the boxes. Fast, strong, tall, great tackling, great positioning, great passing, calm in possession, leadership. There are no defenders that tick all the boxes. You have to concede somewhere. Ten Hag needs players that are good in possession and pressing because he wants to play a high line. Even the consequence is that he'll have to concede height, than that's a better option for him than to play with a strong/tall defender that panics when he has the ball.
Sure you're going to be vulnerable in set pieces if your playing small defenders. Sure you might struggle in the last 10 minutes if you're 1-0 up and the opponents put it a big striker or put a big central defender forward and try to create chaos that way. But there is no perfect scenario in where there are no risks. There has been no team in history that had no weaknesses. Barca's tiki-taka team had 10 midgets and Pique. Even the goalkeeper was a midget. They were very vulnerable in set pieces or if they played a team that could actually get to their box. But this did not happen very often. Of course ideally you have everything, but in reality the perfect players don't exist. It's about gelling the team together and finding a match between all your players. In Ten Hags philosophy he wants to keep the opponent away from goal. Pressing, aggressiveness, positioning and being comfortable in possession of the ball is more important than pure physical strength or height. If a choice has to be made, therefore he'll choose to sacrifice height.