I think many GUE instructors themselves are missing the key point of GUE. GUE is a holistic methodology. For some reason many GUE folks completely miss this point. Holistic means: all or nothing. All the divers must be GUE trained and have all the equipment must be according to GUE. Giving advises to folks that are not GUE can be very dangerous.
Suggesting somebody to have a long hose without training can be dangerous. It's better to have short hose and follow OW procedure in this case. Suggesting not to have pony to a single tank recreational diver who dives with newbie instabuddies, while yourself diving doubles with very well trained crew is not right. Requiring a person to clip SPG to the left ring while he is not trained to clip/unclip it all the time is asking for trouble. Etc. etc..
Nowhere in the GUE ethos does it say you must only dive with other GUE divers. This is fallacy which leads others into believing that GUE divers think they are better than anyone else and are some elite agency. Most people I know, regardless of agency, are pretty picky about who they will do big dives with. I know I am, and I don't limit myself to solely GUE trained divers.
For recreational MDL/NDL dives shallower than 20m, I will pretty much dive with anyone. There is a wreck surveying and mapping project that I am a part of. Yes, it is managed and run by a few members from GUE-UK, but it is open to anyone certified to partake in. We have 2 boats going out on the next project weekend in October with 24 divers trained by at least 5 different agencies (GUE, PADI, BSAC, TDI, IANTD), with experience from newly qualified BSAC ocean divers to divers with tech certs from a variety of agencies. And I can guarantee we'll have an awesome weekend.