Interesting indeed. Yes, I do know how to buddy breathe. In OW I was only shown how & did not do it. Once I started training in technical diving, it was mandatory. In fact we had to swim 4 pool lengths with no mask, in full technical rig, while buddy breathing. Not easy,.... especially during turn arounds.
Thats what we had to do in 1970 for the NAUI certification being taught us by a club, the Atlantis Rangers. And to really get us hating life we had to sucessfully complete the drill using a double hose reg and then a singal hose reg as it was unknow which we would rent or buy so we had to be prepared and learn how to dive w/ both types of gear. those who went thru early certs didnt have to feel left out when advanced certs appeared. We were not shorted any training thru Naui in that class of 1969-1970 unfortunately there was a high attrition rate ............. a bunch never contined to check out dive phase.