they are indeed. competent and well done and no disparagement intended as I consider myself one them... in fact I am likely one of the most uncredited and disliked (By HTC and many others) texture map and terrain contributors from the distant past history of AH.
I personally revised the 2d plans from many sources and photographs for the 3d model for the B17g years ago. (the AH B17g 3d model is the only accurate 3d model of a B17 in existence and you have me to thank for the accuracy of the plans upon which it was created by Natedog who was unhappy with inaccurate available 3-view plans back at the time of its construction.) Made the default texture maps for the B17g, B25C, B25H, P39D, P39Q, P38J and did skins for the P51D, P38G, P38J, original P40E and B25C years ago and I always considered my own work very good...
but to me Greebo was always the gold standard prolific skinner that has improved the quality of a mass quantity of vehicle and aircraft graphics for HTC and AH to a level that attracts even an observer who does not play AH to enjoy inspecting his work...
I simply enjoy looking at Greebo screenshots of the texture work he has done due to the intricate detail and realism he is able to capture.