McCain’s inability to raise his arms is obviously not his only problem with his arms. Keyboarding is a complex activity which requires lots of coordination among all fingers hand muscles, and both forearms, plus the shoulders are important as well. It was McCain’s shoulders that got the worst injuries, I believe. He probably simply does not have the time to make use of the generally quite slow computer devices that would allow one to make use of email. The handicapped people I know who use computers with special aids have to work with excruciating slowness. Public figures do hot have that kind of time.
You could be right. As soon as I hear it from him or someone who is authorized to speak for him, I will believe it.
Unitl then, I will just say I don’t know and wonder if (or suspect that) what you say is actually the reason.