md5 password valid and invalid after upgrading

Hello,

Issue:
Unable to log into database with md5 password, only after upgrading remote
system's psql version.

Error:
psql: error: connection to server at... failed: fe_sendauth: error sending
password authentication

Steps:

1. Setup Postgres 11.17 with an MD5 password
2. Access the DB from a remote system that only has psql 9.6
3. Upgrade DB to Postgres15.x
4. Log into database using psql 9.6 and the original password
5. Observe no issues
6. Upgrade psql on remote system to 14.x
7. Attempt to log in and see an error

The documentation regarding Postgres 14 does not specify the old password
will not work. It specifies the default was changed and that *new*
passwords will be stored as SHA256. I am not using boolean-like values for
my current password.

psql14 does not appear to recognize that it needs to use md5 but psql9
doesn't know any better, so it works.