To me currency means that I don't have to think about tasks that previously didn't have to.
To put that slightly better, if I haven't flown for a while, and when I go back and fly again, if I now have to start thinking (even only briefly) about tasks that previously were automatic, then I am not current, and should be with an instructor for that flight.
At PPL level, I should always have space brain capacity, to allow me deal with unforseen circumstances, emergencies, and stupid mistakes. If I'm not current enough, I'll have to think about things I didn't have to think about before, and therefore I'll have much less spare brain capacity.
To me, that is currency, and hopefully between the club rules and my own judgement, I'll always know when I'm current or not.