There's not a lot of benefit to making a public discussion out of something like that compared to the pretty personal ramifications to the person brought up, which makes even the most constructive attempts look vindictive.
That's not to say the author couldn't give valuable advice, especially in more generalized areas like the craft of programming, or even navigating office politics. It's just that any advice will inevitably be specific to Google. It seems strange to offer career advice when you've not had a "career" per se - more like you've had one really long job.
And who's asking him for this advice? Did people get wind that he might be looking for other jobs, and so he became the "career guy?" If so, that's a revealing insight into the culture at Google, evocative of flock animals asking their least risk averse member what he saw on his adventure beyond the paddock...
My understanding is that that's the kind of mentoring he offerred, yes.