I didn't get anything like that when I was applying. I was notified by phone call from my local social security office when I had been approved, days before the letter came (which was nice and they were genuinely happy for me which was also nice).

I would guess non-medical might mean did you work enough quarters, etc although I'd think they'd check that first. I had to go through a little discussion to show that I could manage my money myself because someone had documented that I had trouble at times and they wanted to be sure I didn't need help with that.

I'd call your local ss office and see what that means. They'll know and you might even be lost in some pile of paperwork with a call to you planned.