Scenario #1 - "We need to show favicons in our browser tabs. Lets develop an API that requires every domain be sent to us!"
Scenario #2 - "We need to show favicons in our browser tabs. Hey look, we've already got a service that provides this. We know it collects no PII and our users trust it already."
Obviously the second scenario is flawed thinking, because (of course) it's better to not send that info at all. However, I can easily see how their developer(s) may have arrived at the conclusion that this is still compliant with their privacy ethos.
The fact that the favicon service already existed (and was trusted by users) before this was implemented, makes it much easier to understand how this could have been a legitimate mistake and thus, they deserve the benefit of the doubt.
Anyway, great decision by Gabriel.