I have seen yet no one recommending to remove the second stage from your mouth while throwing up....
And yet, I've been quite successful at it.
There are rules based on science... like don't hold your breath.
There are rules based on tradition... like when I took my IDC, all my students had to kneel.
There are rules based on fear... like you can't use your long hose or airII at a particular resort.
There are rules based on utter BS... like don't puke in your reg.
Rules based on science seem to pass the test of time.
Rules based on tradition often change when we see the damage the tradition causes.
Rules based on fear pass when the fear passes.
There are too many rules based on BS and I ignore them as I discern them. No one has given me an adequate reason to puke in my reg. My own experience is that puking out of your reg is best... at least for me.
It reminds me of the captain that told me that a mask on the forehead was a certain sign of distress and that I owed him a six pack since he saw me with that. I told him that having your sunglasses on your forehead while explaining that to me was a certain sign that he was full of crap and he owed me a fifth of Scotch. It was good Scotch.
Training agencies once called NitrOx "voodoo gas". Training agencies once taught that you should never dive solo. Training agencies still make their instructors do CESAs, which is immoral as heck.