Winter tires?

Right, -1 on diameter and -1 on width for my WINTER TIRES. That's a common setup.
I love the smoother ride when my Bolt is on the 16" Winter wheelset instead of the low profile 17" stock wheels.
I suspect wheel and tire sizes on newer cars are subject to the Style Department and not the Engineering Departments at car companies.

And just to clarify, these are not your like you dad's Snow Tires on the back of the 60's Buick wagon with big chunky tread.
These are modern WINTER TIRES. They are great in snow and ICE!

 

I started with the prime SE, so I just kept 17" for steelies and michelin winter tires were available, so I got those on the car. They work great. Though I do prefer Bridgestone Blizzaks over the michelins.