I don't see a problem. The 18 gauge wire is the fusible link.
We owned a rental house some years ago. We later discovered the last batch of tenants had added some outlets. Yes, you guessed it. All 'new' circuits were wired with 18 gauge doorbell wire.
How come you never find anyone that accidentially goofed up and ran 1/0 on a 15 amp laundry circuit. Oh right. There's that price thingy....
I've heard that the NFPA is relaxing their bonding/grounding techniques and requirements...but I think that's gone a bit too far.