The "spirit" of DIR includes team, planning, process AND gear ... one cannot pick and choose and still be DIR. It's an "all or nothing" proposition ... kinda like being pregnant.
I've heard several GUE instructors posit that you choose gear appropriate to the dive you're planning to do. So what happens if the dive plan involves going someplace you can't get to in backmount?
I'm not convinced that she's entirely wrong. DIR has never appealed to the masses, nor has that ever been a goal ... but it has also never been as hide-bound as some people believe. Over the past decade I've seen several shifts in thinking with respect to gear and approach. No system can remain static in a dynamic world ... that's the path to extinction.
As SM broadens its appeal to the diving community, it needs to develop some standards and best-practices. The agencies promoting the DIR approach are particularly well-positioned to at least examine whether this technique could be used within the constraints of their system, and in so doing become an important factor in developing those standards.
Frankly, I'd trust them to do a much better job at it than the recreational agencies.
SM is just a tool ... and like any tool there are better and worse ways to use it. It isn't inherently "not" DIR ... it's just that none of the DIR proponents have as yet proposed a way that it could be appropriately used within the tenets of the DIR system. At some point, I think that will probably happen ...
... Bob (Grateful Diver)