I suppose the fewer shared stimuli, the less synchronism. So new asynchronous and low stimuli communications ways as Whatsapp or social networks loss the potential benefits of this study.

I am not sure about this. I talk basis on my personal experience, but typing is write things you listen. Handwriting implies listen, summarise and write (you are slower than conversation so you need make a just in time summary). Also handwriting is not only write text, I usually add non textual information like draw schemas, symbols, complex formulas, link with lines… implies a mental work that typing hasn’t it

I think probably paper could disapear, but it will be replace by handwriting in digital devices. I have replaced my notebooks by the kit iPad+Goodnotes+Apple Pencil. The experience is very similar and it has some advantages. I still prefer physical books to read, but as new generations start to read school books on iPads, this will be the end of physical books. So I think paper as default support for books will be replaced, but handwriting will be present in digital devices.