> All failure, rebuild, and reindex cases will be reported by pg_upgrade if they affect your installation; post-upgrade scripts to rebuild tables and indexes will be generated automatically.
Not true. Those scripts only cover problems caused by PostgreSQL itself, not, for example, a change in collations that will silently break your indexes, such as the one in Debian 12.
It's a step of your script or runbook. Right?
It is, but it also takes a very long time during which production data integrity can be severely affected.