True, but AB generally dictates an 0deg axis setup for each microphone, rather than adding some angle, so it goes both ways. I think it's generally understood that settings like NOS/ORTF/DINa/etc have formal settings, but we bend the rules here on purpose.
I think it's just an easier way to describe the angle/width of the setup as opposed to writing everything out individually (90deg, 30cm, etc). If we, as tapers, operated under the strict recording guidelines originally created, we'd never be so crazy as to take these condensers out in the rain.......or in the middle of Wooktropolis.