Precisely!! I had the same thought. Just seems like a bad idea to make that big a show of it all. But still, hat tip to the guy--cool as a cucumber.
For all we know, he explained his actions to the others during a debrief and explained that he doesn't recommend others handle it that way. Maybe as a dive pro, on a relatively shallow dive, he thought it would be an opportunity to see if he could re-seat a reg underwater--perhaps something he knew was possible but had never tried--and otherwise decided to make a teachable moment in keeping calm out of it.