^^ You’re correct. Princeton and Stanford have not reported yield as of mid-May. However other colleges have
MIT, May 10, 2017: http://mitadmissions.org/blogs/entry/class-of-2021-wait-list
Dartmouth, May 11, 2017: http://www.thedartmouth.com/article/2017/05/class-of-2021-has-record-high-number-of-students
Yale, May 16, 2017: http://news.yale.edu/2017/05/16/class-2021-one-record-books.
Harvard, May 5, 2017: http://news.harvard.edu/gazette/story/2017/05/84-of-admitted-applicants-will-attend-harvard-college/
The new normal, at least for the above colleges, is NOT to include waitlisted students in their yield numbers. Or, maybe those colleges are following Harvard’s lead.