How is it a Ponzi scheme if any photo uploaded before July 2021 will still be stored for free? In such a scheme the last N people to join lose their "investment

How is it a Ponzi scheme if any photo uploaded before July 2021 will still be stored for free? In such a scheme the last N people to join lose their "investment". In this case any new user could easily upload their entire library before then and have it hosted on Google's infrastructure (theoretically) forever, for free.