The other consideration that complicates issues for the holster maker is that GLOCK models 29,30 and 20,21 are now available in a different frame size. It is called the GLOCK 30 SF which stands for "Short Frame" where the frame dimensions are slightly smaller. They do however, retain identical slide dimensions. It is possible that Ring's G 30 blue gun model is crafted in either G30 SF or G30 - causing confusion for the maker & customer.
I know this is heresy on this board - but when making any GLOCK holster, I have found that Kydex is the superior material for the blocky shape of any GLOCK. I use a kydex holster for tactical pistol competition for my GLOCK 21 SF. When I make a leather holster for a GLOCK I stick to a very tapered loose mouthed pankace-type. The stiching has to be just right because of the square slide.