What it established is that when you hire someone, if they have said that they can not work a certain day for religious reasons and you agree, you can not renig just because you want to.
Which was the case here.
It would also follow with other religious accomidations. So know what you are agreeing to before you agree.
Which used to be the standard before the government decided the standard did not apply to them because they were special.
The job applications for everyone, not just the Lost Office, ask “Are you willing to work weekends and holidays?”
No surprises there.