They blocked access in the back end, but didn’t adjust the frontend to deal with this situation.
If you try to access twitter while not logged in the frontend requests tweets from the backend, gets an error response and therefore tries again around 10 times per second.
I don’t think google fear Apple having to offer a choice to users. They fear Apple defaulting to Bing or something else.
While most people might choose google when presented with a choice, possibly more people are just going to keep the default settings when not presented with a choice.