A/B testing is usually trivial and the disclosure will be trivial too. It does not need to be any burden to the readers (like a popup), and with a good tooling

A/B testing is usually trivial and the disclosure will be trivial too. It does not need to be any burden to the readers (like a popup), and with a good tooling (and A/B testing requires tooling) it will not add much work to the developers too. It might be just automatically recorded in a public log. From time to time there will be something more interesting in that log and that will be the task of the media to analyse the logs and discover the interesting stuff. The disclosure just makes this work easier.