I'm *guessing* that the AR coating has some metallic content (again, just guessing), but I think that they said that the AR coating in COMBINATION with a metallic reflector caused problems with the BT signal.

I have no idea how they are coming up with the lumens. I'm guessing (again), that as you suggested, they may be taking the current vs. the existing T08 current (which I understand from BLF thread, is not using 7135s) and then extrapolating the resulting lumens from there. Again, that's a guess.