> but to be effective, they must be measured

Google can't really be trusted to provide measurements proving that they should be regulated, though.

If they want the problem to be fairly studied, they're free to publish their datasets.

Google is not attempting to prove that they should be regulated, they are attempting to prove the that regulation the EU is imposing is not having the effect that EU claims it has. Whether they can be trusted or not will be up to the court in the EU whenever they present evidence.