If I had been in his position, given the results of the survey, I wouldn't have changed the system, either.
It was a dead split among the possible choices, and any selection would've been attacked for it's strategic political consequences, so he did the only fair thing which was nothing.
Also, "counting promises as equal" is value projection. The severity or weight of each promise is subjective to each of us (single-issue voters are still a thing after all), so an unbiased, matter-of-fact counting is not a way of equally weighting them.