As someone treats these for a living, this is unequivocally a bad idea even if we assume autopilot is perfect. There was a real risk of him dying behind the wheel. loosing consciousness. In pain like that you think he has judgment to safely no when to override the autopilot?
To the posters who mention he shouldn't pull over and talk on the phone. In the slate article he admits to texting and using his phone normally for auto pilot. He did call he wife so at least she would have known what happened.
People do this all the time. Worried about how long it will take, not wanting the hassle or the expense . I get the latter concern but not the former two.
If you think you have a PE, heart attack, stroke etc don't drive or get your buddy. Call 911 or the local equivalent.