If the ability to remove apps obligates them to remove apps, then that is a strong argument for them not to have the ability to remove apps.

It also almost certainly doesn't so obligate them. They aren't acting as an intermediary, they are just incidentally signing the app. The app signing certifies in the first place that they checked the documents of the app devs, and in the second place that they haven't decided to remove the app. But removing the app is an action, not an inaction, they can't be compelled to take it. It would be like the record label saying I had to stop a bootlegger I happened to observe while I was out for a walk.