Add option to not let websites use Accelerometer and Gyroscope data
You are correct that it should be possible to disable this. However, Android's WebView doesn't agree with that assessment. As such, I will have to wait until the release of Privacy WebView in the 4.x series to address this.
(If you look at feature requests for the 4.x series, you will see that there are a number of them that relate to preventing fingerprinting that can't be done without Privacy WebView.)