In my experience a lot of YIMBYs are actually NIMBY but YIYBYs - Not in my back yard, but yes in YOUR back yard. A classic example is so-called progressive Robert Reich who has many times opined about the lack of affordable housing, eg,

https://www.commondreams.org/views/2020/07/22/time-invest-af...

But strongly objected to a plan to build affordable housing in his own neighbourhood:

https://www.johnlocke.org/good-for-thee-not-for-me-robert-re...