I’ve always found GN pads to be massive in comparison to other pads, and the straps stupidly long. I’m 6ft and find the regular men’s GM pads to be perfick.
Ummm... 2003 I think.
So in summary, GM, GN and just about every other brand are either small or large.
I’m not sure the lack of standardisation is the issue. It’s more the way the manufacturers size them. You could have two people the exact same height, and one might need small men’s, and the other large men’s, solely due to the length of their leg between foot and knee. Rather than calling them small men’s, men’s etc they should sell them by measurement, say ankle bone to centre of kneecap, similar to how you buy trousers not only by waist measurement but also by inside leg length.