I think that brings up a good question. Where is the line actually, between recrational and technical?
I don't recall ever seeing it defined clearly. In my mind I've thought that deco is sort of the defining difference of technical diving
but as I type this it comes to mind that overhead environments might be considered technical too.
There was no official definition of "technical diving". Michael Menduno (who sadly had a stroke this week) coined the phrase and he took it from "technical climbing" which was climbing outside the norms of traditional climbing. Climbers have exactly the same arguments about what when climbing becomes technical climbing too.
I was lucky enough to get into technical diving in the early 90's at a fairly young age. At the time it was generally considered anything outside of "standard" recreational diving eg. beyond 40m, outside the NDL and/or using gases other than air. You could also include using equipment other than open-circuit scuba. There were discussions even back then as to whether or not basic nitrox use was considered technical. For context, the recreational dive industry was extremely hostile towards things like decompression and particularly nitrox. At one point DEMA banned anyone who was involved in the nitrox industry so nitrox divers were outsiders too.
To add to the confusion, outside the sphere of influence of organisations like PADI, air decompression diving was fairly standard practice for recreational divers. It was part of BSAC, ScotSAC and SAA training here in the UK if I remember right and I'm pretty sure it was the same for the European agencies too. Does that mean deco dives are not technical dives?
At the end of the day, "technical diving" is an arbitrary phrase that's kind of morphed into a commercialised marketing term now. It really only matters if you're selling something. People did what is considered technical diving long before it had a name. They just called it "diving".
As to whether OHE diving is "technical"... I'm a British Cave Diving Group member and the logo on my hoodie says "technical divers since 1946" so I'd give it a yes. So much of what fed into open-water technical diving came originally from cave diving that it seems silly not to include it in the "technical" category. But then I think these days "technical diving" is a silly term itself because the whole thing is so normalised. If you weren't involved in the 90's then it's hard to appreciate how much of an outsider sport it was whereas today it really is nothing special to hold a trimix cert.