I guess I should be happy that someone agrees with at least one thing I say....

I agree with you that lux and lumens are good to know and compare.
And agree that the distance from the source is required to give any meaning to the claimed light intensity.
Of course, there is marketing... we do not always get that info. Others may disagree.

I recall that the inverse square law applies to a point source of radiation.
I'm pretty sure light falls off less rapidly when well focussed... (extreme case of shining a laser spot on the moon)...
Any light source, at a sufficient distance, does behave as a point source (divergent beam)
Others may disagree.

Overall bike light brightness: I was refering to, then and now, the brightness with "off the shelf" bike lights.
I think they are (on average) brighter now, due to LEDs and batteries. Others may disagree.

It's probably true that a bike light cutoff would work best if all roads and trails were flat,
so at 50 feet, the light intensity created in the first 2 ft above the ground was bright, and much less bright above 2 ft.
Since the world is not flat, having a bike light cutoff is sometimes no help at all. Others may disagree.

I like the idea of having a cutoff, I'm not saying to make them mandatory, just a choice.
Others may disagree.