Why is this bad? On first read, it seems like it could replace personally identifiable advertiser cookies with a trusted assertion that I am a human. Feels like a win

A lot of that stuff is pretty standard if you're doing logging and metrics on your service (which you should if you want to resolve outages). From the IP address and user agent you get rough location, os info, and network info. A few other things can be used for optimization (faster load times), and a Meta-scale, I wouldn't be surprised if they do that.