Hi, Patrick - a link to the adopted rule change is here
(and I will amend my original post).
My example of your tournament is a somewhat incorrect, as the three criteria for counting starts for club dues for a multi-race event are (1) same day, (2) same venue, and (3) single entry. As you point out, SART has all its events at different venues. A more realistic and financially constrained example would be a school orienteering demonstration where participants run multiple small courses (e.g. a maze-O). The standard start fee could be prohibitively onerous for clubs to sustain these.
It should be noted that the rule change is designed to give flexibility. Clubs can use whichever of the two options they wish. If SART had multiple races at the same venue, then I think it would be reasonable to use start point (2). My interpretation of the rule would be that the example you give - of 3 races on the same master map with the same event HQ could be interpreted as one "event start" under dues rule 2.
Club dues are confirmed with the director of membership and accounting (currently Robin, but we are transitioning in early 2018). Sandy Fillebrown is the de facto current "director of membership." Clubs must document how they are allocating their starts, of course, such that the director of membership is satisfied.
Ultimately, these multirace events are a minority of our starts; I voted for the rule change to remove any possible financial obstacle to holding these, especially for youth. I don't expect it to have much effect on OUSA finances.