It's not the only technical control they have - every single datapoint an app can gather is ultimately provided from the OS. They could let you disable access to metrics that have proven to be useful for fingerprinting. They could also attempt block known tracking code - all games with IronSource ads will run the same tracker binary, byte for byte. There's a lot of things they could do, but don't, since in the mainstream they have a pretty good reputation when it comes to privacy.