GAW,
The difference is not intent (subjective) but context (objective). Playing arcades with your sister-in-law on an outing with your wife and children there is not ???????, but playing the same arcades on an outing just the two of you would probably be schok. The difference isn’t the type of Erva but the context. Do you think that it is mutar to have a date-night at an arcade with ishto niddah? If not, how is a dating couple different?
I believe that the “dibbur” in the Ramah and the Shach is going on Kalush Rosh and the point is that flirtatious talk with an Erva is assur even there is no actual intent to be margil. For example, some salesmen will give inappropriate compliments to female customers in an attempt to make a sale. That would still be kalus rosh.