Voluntary exits are pointless if you're planning to lay off the entire team. It usually means that they're keeping part of the team, and want to make sure that they keep the part that'll actually stick around.
It's most likely an attempt to give low performers (if you received a bad rating for last year) a chance to leave on your own terms before they lay you off.
If I was in that bucket I would definitely take this offer.
Looks like all the large tech companies are doing aggressive stack ranking right now.
The job market is terrible right now. More likely the high performers will take the offer because they believe they have better chances of being rehired somewhere else. Good luck to them though.
Assuming the events are independent, P(you get laid off) x P(you don't find a new job) will always be less than 1.0 x P(you don't find a new job)
If I already had a solid offer somewhere else, I'd take the severance. If I didn't, I wouldn't leave it up to chance, and I can't imagine many other people would.
With only three weeks to make decision, my guess is high performers aren't going to start looking for new jobs now unless they were already looking to begin with. From the wording of the message, it sounds like Google is okay with losing the group that was already looking.
The rules are complex but if a company wants to lay off many people in one ___location they have to give notice in advance and usually choose to just payout that notice time.