That first sentence doesn't really mean anything to me as it is stated. While I was a software engineer in a previous career, I've never written code for Unity, so maybe the sentence would be clearer if I had.
What I do know many of those triggers are relatively new in the life of 7d2d POIs. That is, you started to get them in 1.0. The minscript feature is pretty new too, and I think that's probably the work of TFP developers, not Unity. That's speculation on my part based on my POI/Mod experiences dating from A19. I'm not privy to TFP's engineering decisions so I have to guess as my only method for filling in the gaps.
That is to say, we've had trigger volumes for quite a while, but we've not had key racks, buttons and minscripts that let them do things like make a volume spawn waves from the same sleeper placements, make cool sounds play, make things explode, etc. When minscripts came about we started to see much heavier use of these advanced tricks and TFP's existing POIs got refits, as they tend to get a little attention with each version.
I realize it might seem weird to characterize a feature that arrived a couple of years ago as new, but I don't recall triggers having a huge role in A19, A20, A21, and I saw 1.0 as when they started to ramp up. Though time and my memory can make things cloudy, so maybe I'm just not remembering things correctly.