There may be a mix of procedures and expectations... I dive primary donate, and generally only with primary-donate-using buddies or at least those aware of how it works. The other week, however, I joined a dive as a buddy to a quite inexperienced diver doing her first night dive as part of AOW. She was not familiar with primary donate, or BP/W, or doubles, so the "BWRAF" became slightly confusing at times. Anyway, the point that surprised me was that she really wanted to test-breathe my "octo" (i.e., long hose). I suppose this might make sense with the traditional rec setup where approximately nobody else is going to breathe from the octo in question, but it did make me slightly uncomfortable having someone sucking on my clipped-off long hose on land.
So I can understand that if someone thought this was the expected procedure for primary donate, that they would be uncomfortable with it.