EDIT:
I was wrong, it's not postgres change, it's change made in "official" docker image, which in fact is not official and maintained by "the PostgreSQL Docker Community". My apologies to pg people.
They "the PostgreSQL Docker Community" (not affiliated with Postgres in any way) did exactly zero checks so users will shoot themselves in a leg in two ways:
What the actual fuck. Why on earth you couldn’t do a simple fucking check that old directory exists and has data, but new directory is empty, and then start with directory with data spitting warnings that default has been changed and you need to do something about that.
This is utter incompetence and giving exactly zero fucks about your user base