It seems like what a college does re ED depends on what it thinks will happen in RD. If they think better candidates will show up via RD, and that they will get good yield out of a decent percentage of them, why fill up the space via ED (especially if they are concerned about the economic bias inherent in current ED process). On the other hand, if they think that the ED kids they are seeing might choose to go elsewhere in RD, why not snag them and have a class with lots of people who’ve affirmatively made the school their first choice. I think both approaches are defensible though the trend does seem to be the latter.