It's not so much about the compass right now, but the idea of cut and dry standardization. If standardization were black and white, then there wouldn't be much to argue about, as something would either be DIR, or not be DIR, sure. But the fact that CCR has been introduced by GUE kinda' contradicts the idea of standardization, and the philosophy of having a configuration that applies to every type of diving, rather than specializing your setup for different dives. If the rules can be bent for tech dives, then why not recreational dives as well, is the question that pops up.
If a group has a very cut and dry, all or nothing approach to standardization, of course people are going to ask questions if you introduce something like CCR, which is a radical change in that standardization. I imagine that's why GUE took so long to introduce it into their curriculum. It might be a lot easier to just call someone a troll for asking questions that are hard to answer, but like TSandM said a few pages back, all choices should be able to be explained.
The answer is probably as simple as, "Rebreathers offer a large enough benefit to warrant changing standardization for certain dives, whereas changes like compass placement, AI wrist computers, and others are more insignificant changes of convenience." Which is fine, and a perfectly sensible explanation, but it still would mean DIR is no longer fully standardized. Much more standardized than any other style of diving, for sure, but not so black and white. The philosophy would be more like, "Standardization for all types of diving. Unless the change provides enough benefit to warrant."
I imagine use of helmets in certain cave systems for safety would fall under the same explanation.
