Any meter marked up as EV is actually measuring LV
With ISO 100 film, the EV required is the same number as the LV measured.
I suspect that at one time, Mr Adams had a meter which only measured in foot candles so this system was perfectly workable for him. Now there is not much point as you have to use a meter either way so it might as well be what we now consider to be a normal photographic light meter.
EDIT: Just to take issue with myself. When I wrote "Light meters have never indicated EV" that was not 100% correct. A lightmeter can indicate which EV to set the camera to if it has a means of entering the ISO value but it does not give an EV level as a measure of light.