It doesn't matter which it is, what I was using before didn't have it.
But beyond that, it refuses to tell me why it isn't just doing the right thing and none of the big systemd advocates here can seem to tell me how one might fix it or work around it.
Beyond that, the thing that is hanging up shouldn't exist in the first place. It has no business caring about anything but the identified (implicitly) dependence on /dev/disk/by-label/aux. Since that is present, it should attempt the mount. Were it designed with an appropriate philosophy, the part that is causing the problem wouldn't exist at all.
The way systemd seems resistant to workarounds is a real design problem IMHO.
All I see on various mailing lists is systemd people deeply confused and at a loss as to what should be done about this and similar problems that the old init system has handled flawlessly for a very long time. That suggests that systemd is not ready for production use. If there was a decent workaround for now, that could potentially be forgiven, but I have yet to see one offered.