Buddy diving and self-reliance was taught in my 1962 Scuba class, long before OW existed. Everyone learned to buddy-breathe since there were no octos and most regulators were double hose. It was understood that buddy teams would get separated when vis was low, the surge was up, and the kelp was thick
duh.
I was in a four-week Navy Scuba class eight years later. They didnt teach anything about how to be stay together, nor was it necessary. The rule was simple. They had these 4' long pieces of die-lock anchor chain with links that were 3-4" wide. If they catch you separated from your buddy anytime during the work day by more than arms length the team had to carry the chain as a reminder. They only grace time was in the head, in-water training, and when class was out for lunch. It did include runs, calisthenics, and classroom. We figured everything out we needed to know about keeping track of each other all by ourselves.