Raven , you raise a very valid point , but safety sadly is driven by lip service and money .If RH was a manager of repute he would not have needed input from the training dept he would have taken action on his own on the merit of the issue.
so let’s take a worse case scenario , a brand new SO is on his own in the flight deck whilst the FO takes a toilet break . Explosive decompression occurs , the supplementary CA sitting in the jump seat has no Oxygen supply so has passed out by the time the FO tries to get back in .
Thus the SO may have to manage the entire process on his own not something that fills me confidence .