In general Google engineers don't tend to work on branches, especially long-running ones. Incremental small code reviews are the expectation. The general process would be to stick things securely behind flags and continue development without turning it on, even if it never ever launches.
Not saying this work should be done -- it shouldn't -- but code being pushed is not the same as "we're going to make this happen tomorrow, no matter what."
Yes, because that's a such anti-consumer issue. It shouldn't exist in the first place, it should never be merged to master. There's no reason to not keep it on a separate branch if you don't intend to use it.