This package installs a cron job that affects how apt functions on your system. You're basically giving google root on your machine.
They're probably accustomed to trusting their own software with root, so didn't even think about it.
Also, can't this be said of any package you install through the package manager? If you install it as root, then in principle you're giving root access to whatever is in the package. If you don't like it, there's always a way to run it with ordinary permissions (but the extra fiddling to get that working may be hairy) or under mandatory access control (definitely hairy).
Nah, it was probably just developed for internal Google consumption.
Installing a repo & apt key is a good sign that they're playing by the rules rather than trying something sneaky.