Studies are not ad tracking. It's worse and more like a backdoor for A/B testing of browser features. A few years back an update broke the Metamask extension and it was fixed by pushing via studies. At that point users weren't very aware the feature even existed and it caused some backlash since users realized there was a backdoor to push code into their browsers.

The backlash resulted in studies being opt-in, and I thought it still was but I don't know, I use "policies.json" to setup my browsers.

> And as a bonus, those were added and activated as features via update, without telling. At least for me.

Ouch, they were new to me and also activated.