if it runs on gas and has blowback it is a gbbr, not sure why folk think differently, the end result is just achieved a different way to convention is all.
My GHK G5 runs AEG barrels and hop bucking too, is still a gbbr, it is just easier to mod then others that don't!
Right so it classifies as a GBBR because of what it does but people don't see it as a real GBBR because it's achieved a different way that makes sense lol,
And I'm telling you from owning the WA and WE spec versions, that neither will work on an AEG spec receiver, I have tried. The pitch on the threads are considerably different.