It seems to me this is much ado about nothing.
The idea that "recreational" can have a meaning as an adjective within a particular domain seems to offend some folks' sensibilities about how language should be used. That really is a personal issue that has nothing to do with diving and everything to do with their inability to segregate terms into various domains or to appreciate the development of language.
In a practical sense, diving instruction today is largely modular. This has created a number of large benefits, including increasing the number of divers substantially. It has also created a number of challenges, including putting a large number of divers in the water who need additional training in order to do challenging dives that older divers with monolithic courses might have been able to complete without more training. More likely the education would come in the form of mentoring by more experienced divers.
With the change in education there grew a need to describe the type of dives which particular students would be able to make that would be within their level of training and experience. One of the primary distinctions became dives that did not have direct access to the surface and/or which required equipment different from what open water students would typically be trained in and which is most commonly provided as rental gear from resorts.
Personally, I find the term to be rather easy to grasp. A recreational golfer can have a wide range of skills and there's no real expectation that they could do well on the toughest courses around. A recreational cyclist is not expected to have the endurance to compete in a 100k race, even if it is a fun race and not a serious competition.
Likewise, a recreational scuba diver is not expected to be able to dive in conditions demanding high levels of skill. That is not to say that no recreational scuba divers have high levels of skill anymore than saying someone is a recreational golfer means they can not have a 2 handicap or that a recreational cyclist might not be able to complete a multi-day 500k race.
Meanwhile, a golfer with an a highly refined approach and short game is often referred to as having a great technical game. A cyclist who has refined abilities is often said to have great technique. To say that a scuba diver who has taken additional courses, is using more complex gear, and doing dives of greater complexity than the typical recreational diver is doing technical dives, and by extension is thus a technical diver is not some aberration of language. Indeed, one of the definitions of "technique" is precisely the systematic procedure by which a complex or scientific task is accomplished or a particular command at handling such fundamentals. A dive requiring command of sound techniques, comprised of systematic procedures and/or scientific tasks is technical.
It's not really a hard distinction to understand. Moreover, it serves a useful purpose in delineating training levels.
Certainly there is some arbitrariness in the distinction. But all language is arbitrary associations of concept and symbol. "Set" doesn't have 464 distinct definitions because of some objective association. It's just the sound and associated letters that came to be associated with a wide range of concepts.