Free apps remain in the store even after your developer membership has expired.

Are you sure? JWZ reports otherwise: https://www.jwz.org/blog/2012/06/dali-clock-back-in-the-app-... (check 'graph 3)

Did that policy change in the intervening time? If it did, would you provide a reliable citation? :)

10 months ago I accidentally let my membership lapse, and I am pretty sure that only the paid apps were pulled. If I am not paying attention in January maybe I will test it again to confirm this winter.