When last time did we have a two-footed player from the academy to make a debut? I can only think of Pogba who is also comfortable with both feet. We had many strikers going up through our academy but none is comfortable with two foot, many of them are right-footed and few left footed. Greenwoods is just two-footed, you have no idea how it is rare for the striker to be comfortable with two foot, he looks like he has a killer instinct to score a goal anywhere, even with both feet
So if the likes of Lingard, Alli, Rashford who is right-footed, it limits their goal opportunity if they felt need to stop and use their right foot to score before it is too late. For an example, Ali had a golden chance against us last month but couldn't use his left-footed then had to cut with his right foot, the ball goes saved by De Gea, that's why two foot is far more valuable.