I don't work at a FAANG company, nor have I ever been to SV, nor do I know anyone who works at one of the many enormous tech companies around SV.
In the TV show Silicon Valley they have characters who sit around unassigned doing nothing at the Google-like company in the show. Does this actually happen? Are there people hired at these companies who just don't have a project? Its entirely feasible that Google could afford to do this just to create a dearth of engineers in the area.
What happens is that some people work on projects that never see the light of day because they’re not fully thought through or fully staffed or really as important enough. But they can still spend years working on them.
The show is (by design) over the top. But there is a piece of truth in it. That’s why it’s funny for everyone who has been at these companies because everyone can see real-life resemblances.
Before someone downvotes me: I am implying that SOME people are like this. By no means the majority or god-forbid everyone. Resting till vesting is a real thing though.
I have, in the last year, twice been hired then found myself way under-utilized because the company wasn't really ready to do anything with me, or the thing they hired me for fell through, or whatever. A few years ago I was brought on to a mid-sized business software company as part of an acquisition, and in the short time before I ran away was used at maybe 1/8 capacity in the most anti-productivity low-wall-cubicle open-floorplan office I've ever experienced.
Organizational/planning/managerial waste of expensive developer time is real and huge. I'd be surprised if companies the size of Google didn't do similar things some of the time, and if their management's a little more clueful than average they might even make such light-weight or non-assignments official and highly visible to make them easier to account for.