When my S and I visited Williams for admitted students days one of the admissions officers mentioned something like that. She said they had had an analysis done and they knew pretty well who and how many accepted students would matriculate. I had always assumed that the numbers colleges accepted were just based on historical yields, but apparently it is far more complex than that.
Clearly they were very secure with the accuracy of the analysis because they were the only school that openly flaunted a “hey if you want to come, great, and if not that’s fine too” attitude.