I've had a chance to look up the appropriate regs:
ECE 48 (96?? Ah - 2x48...)
Interestingly, the regs now talk about lumen output of the dipped beam headlamp unit and not the type of light source:
"...Dipped-beam headlamps with a light source or LED module(s) producing the
principal dipped beam and having a total objective luminous flux which
exceeds 2,000 lumen shall only be installed in conjunction with the installation of
headlamp cleaning device(s) according to Regulation No. 45." (6.2.9)
With high-output lights, the regulations on vertical control are stricter, and so automatic levelling systems are required.
So it may well be that the Subarus and Mitsubishis, although having HID lights, do not output >2000 lumens and so auto levelling and lamp washing is not required.
I was interested to see that the regs have been updated since I last had cause to refer to them - they now include conformance and installation regulation for cornering, adaptive and LED lighting systems. The use of fail-safes (such as the brake light being used as an indicator when the buld fails) is explicitly broken out too.