Sure, if what you mean by "a culture with low levels of (expected) politeness" is one in which there is one standard greeting, X, with which you greet people "regardless of the situation," then you're absolutely correct: that is not at all idiosyncratic.

I guess I misunderstood you: I thought you were proposing an approach where people just greet one another however they wish and they don't worry about etiquette at all, rather than an approach where there is a single approved way of greeting everyone.

The former I think does lead to idiosyncratic standards; the latter I agree does not.

Sorry for the confusion and thanks for the clarification.