Having an automatically added tag for any stream with pre-rolls currently disabled (through automatic ads or with the new automatic ads) would help drive discoverability towards those using this feature.

I feel it would also encourage more streamers to use the ads appropriately during low activity moments or when they take a break from the stream, thus also increasing revenue.

By having it as a tag that will be automatically added (and removed) it's easy to filter for streams that have the tag within a category. From conversations with my viewers, they would definitely be more willing to check out more creators when they are sure they won't be presented with long pre-rolls before seeing if that creator is right for them or not.