Not sure why this is an issue, normal operations would allow one pilot to leave for a comfort break. Two things I have concerns over, one the FO posting a video and secondly why has he not put on the oxygen mask when the captain leaves the cockpit. I thought that was a SOP requirement.
Sadly the captain is going to get a kicking and the FO will not have his contract renewed.
Well this proves you can't teach common sense... shame.