On one level this is amusing. But what if both accounts are owned by the same person impersonating Neal Stephenson? My understanding was that he was not on any social media. Did that change at some point?

Assuming https://nealstephenson.com/social-media.html is real, he has social media accounts (linked from that page).

That domain has been registered since 2000, it's probably real.

It links to a google plus account, it's probably not updated promptly.