Yes, I remember receiving mail that late in some cities.
The PO does not treat its peon employees very well.
That may be so, but in some locales (such as the one here) one or two postal workers in the main office act like it's some kind of major favour to have to move their wide loads a few steps away from the counter and collect your mail just to step back and hand it over to you. Including demanding "proper ID" each time even though you've been going there for several years on.
Not saying anything about the individual in question, mind, but do not make the mistake of thinking that just because someone works for the postal service there is nothing else going on there. In this case, I would guess the neighborhood, and if true, then the postal service would have been well within its rights to refuse delivery due to an unsafe environment.