Terrible advice. The FAANGs are highly competitive and people are eventually going to notice that this individual is not at the average job level they should be at relative to their years at the company. That will eventually make internal transfers very difficult (yes, hiring managers do check for duds for internal transfers) and motivate their management chain to wash this person out of the company as good attrition.
Maybe they are at the average job level but just aren't feeling challenged? They did get a promotion, so they can't be that bad... Maybe they're just bored? Either way, leaving a secure, good paying job is almost always bad advice, especially without a firm plan in place..
While L4 is terminal at Google, it's still not particularly high achieving for 6 years of career. Google also doesn't make it easy to jump from L4 to L5 either, so OP may feel like they're stuck in a rut because of that as well.
100% in agreement. One major risk you’ve accumulated by slacking is that you may not easily get another job if google does eventually push you out. Your next employer will say, tell us what you’ve done - specifically. At some point you either have pride and integrity as a person or you’re an asshole. Google might tolerate that now when you’re young but I think fewer and fewer others will as you age. It sounds like you have some time to make some changes in your life - I would recommend you start there before kids and other life events take priority.
I won't say that's not a valid choice (I've seen it done) but if it comes down to that, the tarnished reputation is probably going to hurt them more than the money they get. This industry is not all that large at the FAANG level and the people who succeed or at least do moderately well at a FAANG tend to go on to senior positions at other companies. This person probably does not want a bunch of former co-workers around to say "Oh, that person; I remember them. A nice enough individual, I suppose, but no hire."
On top of that, the wash out process isn't likely to be all that pleasant, particularly if this person has depression problems already. Getting negative feedback and the cold shoulder from their colleagues for months/years is probably very demoralizing even if they are still drawing a big paycheck.
One promotion means he is L4 minimum, which is now the level which Google no longer requires you to move up. As long as he is getting "meets expectations" with the occasional "exceeds" every three cycles or so, he will be able to coast at the big G for a long time.