Not true at all. There's a large part of brain development that comes from simply practicing handwriting.[0] Putting pen to paper is a huge part of language mastery. In most educational situations, that practice is going to occur outside of the classroom as there is simply not enough time in the typical school day.

Even in the study mentioned in a previous comment [1], the authors disagree as, "we find additional homework to be most effective for high and low achievers".

[0]https://well.blogs.nytimes.com/2016/06/20/why-handwriting-is...

[1]https://www.binghamton.edu/economics/research/old-working-pa...