Theres nothing confusing mate, we don't refer to any other type or era of music on THIS scene as crossover. Well I don't and I don't hear other collectors or dealers use it to describe anything else, I don't see it on sales list or playlists either. For the intents and purposes of the UK soul scene crossover is the period we are talking about here.
If it's 60's maybe white, the example you give it's simply northern soul. I don't hear it described as anything else, apart from the occasional, pop and sh*te If it's 70's and a dancer it's usually described as such, a 70's dancer. Same goes for R&B etc etc. Simple really