The article cite studies that handwriting is linked to brain development, and reading on paper improves memory, and so on... I'm certainly not in a position to refute those studies, but I have to wonder how complete they are. People once denounced the printing press for causing us to loose our memories, and as a population, we do in fact have worse memories than scholars during the Middle Ages. If we taught intensive memory training in school, memory would likely improve, but do you think that would be an ideal use of student time?
Maybe handwriting is a magical art that improves brain function across the board, but I'm going to need a lot more evidence before I believe that. In the meantime, we should be teaching the skills that people need in today's world, and that overwhelmingly means typing.