Unwritten rules or, perhaps another way of stating it, the penumbra of the rule set
As an extension: Play to win doesn’t have to imply that you’re trying to win for winning’s sake. It is also reasonable to incorporate play to win strategies to serve a larger goal – a goal that you set. Play to win strategies do not defin what “winning” is – only you do. Yes, “scrub” playstyles can win the match but perhaps you’re not trying to win the match but rather trying to win a loyal following or aclaim. Scrub playstyles, in these situations, may be sub-optimal. Play to win only requires you to identify the optimal strategies within the rule set, written or un-written, and employ those in pursuit of your goal.