As I see it, the need to precisely define the boundaries of rec diving is a product of the major training agencies' push to make available to the masses the kind of diving that the masses want to do. Most divers are not hanging out on SB or some tech diving forum. Rather, they're traveling to warm destinations and enjoying the underwater world for a little while. The major training agencies devised programs to make that easy and safe, and the boundaries they have drawn around that realm define "recreational" diving. PADI may have been the biggest proponent of this concept, and so the term "recreational" may be somewhat American-centric in origin. As pointed out above, BSAC felt no need to define the boundaries quite so precisely, and probably other agencies as well. CMAS?
It is worth pointing out that PADI -- per usual -- has tried to define safe boundaries, for example PPO2=1.4 as a limit. They argue that 130 from the surface (whether straight down or partly into a cavern or a wreck) is another limit, with the added complexity of the overhead. They argue that Nitrox below 40% is safe. Going beyond those conservative limits requires more planning, more experience, more training, more gear.....
Going beyond those limits may not be dangerous, but it is certainly raising the risk profile. Some agencies say even those limits need to be pulled in further, like GUE not exceeding 100 ft without He.
Those who argue that depth is irrelevant are living in a fantasy past, when He was not so normalized, and you never ran out of gas. Bounce dives? Silly, unrecognized by any agency, not part of recreational diving. Calling a pony your reserve is childish semantics; most would call a pony an emergency gas, NOT to be used as part of your gas planning. That is how the agencies train people to use a pony.
Two things are clear about tech diving: you plan your dive, and you have the necessary redundancy. Dropping accidentally dropping below 130 ft does not constitute a tech dive, because it was not planned and it did not have the necessary redundancy. Tech diving is, well, more technical, both in terms of the planning and in terms of the possible equipment.
The Solo card from SDI and the Self-Reliant card from PADI are, I submit, very close to technical certifications, even though they do not exceed "recreational depths" and do not allow deco or any kind of ceiling. They DO require planning, and certain redundancy in equipment, including gas supplies.
