Others have already commented on how this isn't "standard" in places outside the US, so I'll focus on something else.
Ted, you're a Big Deal. You maintain ext4, you're a major kernel contributor. Of course Google is going to keep you happy, give you plenty of time to work on FOSS, and provide you with resources for it. They are paying you to work on FOSS to a large extent. The deal is they give you all this time and resources, and you slap a Google copyright on it and don't care because it's all GPLed anyway, and since you're working on this stuff at work anyway, you throw everything into the same bucket and Google owns whatever commits you make at home too.
This is entirely different from the average Google SWE/SRE, who may have a number of personal projects, and may contribute to random things, but nothing Google cares about much. Google doesn't give a damn if I stop contributing to FOSS. As an SRE, none of my work product at Google had anything to do with FOSS directly (except, like, one 20% project where I ported Linux to some vendor hardware). Google doesn't care if they force me to stop maintaining usbmuxd, which they effectively did by rejecting my IARC application (without answering my questions after it; e.g. they could've proposed going through releasing and Google copyright from then on, but they also didn't do that).
For someone like me, going through all those processes, especially in the form they existed in back when I worked there >5 years ago, was all red tape for zero benefit. Google wasn't sponsoring any of my work. Google doesn't care if I have a commit in ALSA to fix 5.1 audio on a specific Acer laptop. Google doesn't care that I made FireWire not blow up on JMicron controllers on systems with an enabled IOMMU. Google doesn't care that Pulseaudio network discovery now works properly with link-local addresses. Google wasn't paying me to do any of those things. They are just things I did in my own time, as a FOSS user, not as a Google employee. And so, it is not reasonable for Google to own that work, that I do on my own time, that has nothing to do with my job, and to then require me to go through getting permission, and to then slap a Google copyright on all my code. Copyright assignment isn't free. I had to relicense a project from GPL to LGPL recently. It was a simple matter of asking the other 2 one-off contributors and changing the license. It would not have been a simple matter if Google had owned part of the code, which they would've had they not messed up my employment contract in my favor.
Yes, other companies are worse (Apple). That doesn't mean Google gets a pass for being less-bad. It's still broken.