This advice is sound and mirrors advice given by other successful applicants to these high stress interview loops.

I have worked at a few of the "FAANG" companies and have noticed a trend with potential hires who are entertaining competing offers. They will often accept an offer even if they have other offers ready to materialize or under negotiation. The candidate feels that if they don't jump on the offer now, they may miss out. This is rarely the case and I have never seen this happen internally. The company has put a lot of time and energy getting you to the offer stage and they want you to sign the offer letter. You could say something like "This is a big decision and I need a few days to consider it" while the other offers finalize. You could be upfront and say "I am waiting for Google to finalize their offer and I want to evaluate theirs against yours." As I stated before, I have yet to see a recruiter rescind an offer because of this. You could even be quite mercenary, and accept the offer with a start date in a month and then retract if a better offer comes through. I wouldn't do this, but I have seen it done many times.

People like to lump these companies together for some reason, but they are quite different internally. While I was at Amazon, the average tenure of an engineer was eighteen months are a large percentage of initial hires left after nine months. These short tenures were not due to performance reasons. The number of engineers coming in to Amazon from Apple/Google/Facebook/Netflix were far less than those leaving for the same companies. I can think of no team members who left Amazon for Netflix. Facebook and Google represented the majority of departures, with Apple following at a much lower percentage.