I have long said that children who remain non-verbal or minimally verbal after the age of 5 struggle with verbal communication not because of a social or language deficit, but because of a motor deficit. They want to speak, but their motor system does not allow them to.
Take the time to read this blog by a young man named Ido who is nonvebal, but has learned to type on an iPad. His description of how his body works is profound. I will be purchasing his book very soon.
Thanks Ido for this insight.