I've no idea on the state of research about this topic but I've always wondered if this really has to do with the locomotion side of it or if it's more about the fact that writing by hand takes a bit more effort and time.

For example, for taking math notes it's easier for me to write by hand rather than take notes in my laptop (because writing LaTeX takes time). If I spend more time on my notes in my laptop, would that improve retention?