I asked that question at least a year ago - would GUE consider rethinking the trimix past 100’ rule if helium wasn’t available? The other poster just danced around the question.
It means that there are no alternatives to what they think is the "right" one.
I have only the most basic exposure to GUE, but I don't think this is precisely correct.
There's a system, and while the principle is that the system applies as a whole for the best effect, in the end, it's a set of guidelines, best practices, and tools, like any other agency's teachings. It's always up to the individual diver to apply the system to the current situation, given the context and constraints in place. The more complex the dive, the more reason to keep it all together, and, of course, if all the right elements are available (equipment, gas, etc.), then there's no reason to diverge from the guidelines even on simpler dives.
When there are constraints, like equipment or gases that are less than ideal, anyone can exercise option one (skip the dive) or adapt to the circumstances. This happens all the time with GUE divers diving air instead of EAN32 because there's no nitrox available, using whatever rental equipment is available for that shallow reef dive while on vacation, etc. It's a question of keeping the dive within acceptable risk tolerances, not that every tiny divergence from doctrine is an unforgivable sin. GUE standards are for the SMB & spool to be in the left dry suit pocket, but when I don't have a drysuit or a left pocket, I'll clip it somewhere, perhaps being extra vigilant that it doesn't end up as a cloud of spaghetti around me, and go diving anyway.
As for when and how dives with an END over 30m would be acceptable, I don't have the training or experience to say. I suspect it may be one of the more important guidelines since we're effectively discussing how mentally impaired we think is acceptable. It makes sense to me that the default answer is "not at all" and that any exceptions must be considered very seriously. Perhaps the correct answer for the future is that CCR is the tool for dives > 30m; I don't know, but I find it extremely unlikely that GUE as an organisation would change its stance and say, "well, helium is expensive, so now we think an END of 45m is alright".
