2017 Did I get had on my rear brake job?

Hi, I have a 2017 Volt with about 68k miles on it, I've had the car since new.

Went to a local shop I've been to before and have had generally good experiences with for the 68k service. I've known the rear brake rotors have been pretty badly scored for a while now as some other owners have experienced, see e.g. Gen 2 rear brake pad/rotor change, sorry I can't immediately find pics of the original condition of my own.

They said they thought the front brakes & pads were still pretty good with about 50% life left, but that the rears should be done and I agreed to that. They asked if I'd like the regular rotors or the FNC rotors and I asked for the FNC.

First problem I noticed was that about 2 days after the work was done there was a driving rainstorm in my area for the better part of a day. I went out the next day and the "new" rears were covered in rust. But the front 6+ year old rotors had no rust on them. So it seems they at least maybe didn't replace them with the FNC-rotors I asked for, okay not the end of the world I guess..

Second problem however is that now, a couple weeks later after a few hundred miles of driving, I'm starting to notice an odd wear pattern on the rear rotors. I'm unsure if this is normal for new rotors but it looks suspiciously similar to the "rusty grooving" my old rotors had, just not nearly as bad.

I've attached pics of a rear rotor and corresponding front (which again have never been replaced since new), each side looks similar. I'm not a mechanic and don't look at rotors every day so I don't know enough to say if what I see on the rears is normal or not, but my amateur opinion is for "new" rotors they look kinda like crap! So at best I have concerns they didn't put on the FNCs as I asked, at worst that they maybe just turned down the old rotors and slapped them back on. First is rear, second is front:



Any comments or suggestions appreciated, thanks.