Couple of things:
1. I did my YMCA/NAUI-based open water training in 1986. Like a lot of divers at that time, we used "The New Science of Skin and Scuba Diving" as one of our textbooks. (We used the 6th Edition, which had gone out of print a year earlier, in 1985.) We learned how to do air consumption calculations and how to plan and conduct deco dives using the U.S. Navy Air Tables, topics covered in this textbook. (We were NOT allowed to do deco dives during our
training, however.)
2. I did my NSS-CDS/NACD Cavern and Basic Cave training in 1988 in Ginnie Springs FL. At that time, garden-variety cave diving was NOT referred to as "Technical Diving" (obviously, since the term hadn't been coined/popularized yet). At that time, some (Florida) Full Cave divers were diving quite deep using air as a bottom gas and deco-ing using 100% oxygen.
3. Only when I did my IANTD Nitrox training (in 1993, in SE MI), and my IANTD Deep Air and Advanced Deep Air training (beginning in 1994) did the term "Technical Diving" loom large, coined by M2 a few years earlier. I understood at that time that Great Lakes wreck divers had already been diving quite deep using air as a bottom gas and deco-ing using 100% oxygen long before the term "Technical Diving" had been coined.
I agree with
@lizardland: "At the end of the day, 'technical diving' is an arbitrary phrase that's kind of morphed... ."
FWIW,
rx7diver