Right, I agree with your observation. The paddle I use is a kydex paddle that I get from Blade-Tech, and it's the same one that they put on their holsters.
There are some leather holster makers out there who use leather as the "paddle". So there are a variety of material choices in that respect as well.
My experience has been that the majority of the "paddle" holsters do not conceal as well as a pancake, etc., type of holster. The paddle holsters are great for the easy on/off aspect, range use, etc., IMO.