We don't really know what he told them or when at all. So saying they "should" have turned around for Cancun instead of continuing to Houston is really jumping to conclusions.Now, if a doctor experiences distress of some sort and plays his doctor card, I imagine he could pressure the crew to divert a flight, even if the symptoms seem vague and nonspecific. Throw in a self diagnosis of some potentially serious problem that the flight crew knows nothing about...that plane is making an unscheduled landing.
I don't think he had DCS at all - even if the symptoms resolved with HBO.