I assume the ads are embedded in the radio stream by the radio station. For one station, I mostly get ads about the audicy app which is the preferred app for the station. For the local classical music station, there’s always an ad for a bank that is major sponsor. It’s also doesn’t happen with all stations.
Interesting about the Tune-in app. I almost always get ads when I use GVA which usually uses Tune-in. For example, I’ll get an ad sometimes before I play Radio Paradise on Tune-in, but never B&O Radio. I would say it definitely varies by station and possibly location.
Stan