You are right but you have to take into account that he was developing plus his head wasn't here and Jose didn't fancy him either.Transfermarkt says he played 17 games under Jose as a centre forward. Not a lot, but also not never.
Van Gaal also started him a centre forward in 15/16 (28 appearances) , then he moved him to the left (24 appearances) when he'd play Rooney up top (and because Memphis was garbage), and later in the season to accommodate Rashford. Most of Martial's goals that season were scored when he played on the left.
in the Jose/Ole season, he played on the left 28 times and scored 10 goals. He played up top 11 times and scored 2 goals.
There was genuine criticism - including from United fans - that he didn't operate as a centre forward when deployed there, his off the ball movement was poor, he didn't gamble at the near post, was often outside of the box when the ball came across goal. All of those things have definitely improved.
I'm not saying he was a shit centre forward back then. Just that he has gotten better at the basics of it, as you would expect a young player to do.
The transformation under Ole is amazing. I think the confidence, the number 9 shirt, and the manager believing in him and helping him with his finishing (because of the manager being a striker) have contributed to the reason why he has started to perform really well