How do you know he was paid to keep all internal details private after he leaves? Do you have knowledge of the employment contract, can you share the relevant language with us?

All he says is his concern about "optics", which has nothing to do with contract.

If Google has a problem with his post, they can go after him, but that's an issue between Google and him, not with you or me or the rest of the internet.

I'm definitely struggling to see what any of this has to do with personal integrity, betrayal, or squeezing personal benefit. To the contrary, it simply seems informative and he's sharing knowledge just to be helpful. Unless I've missed something, I don't see anything revealed that would harm Google or his former teammates here. No leaks of what's coming down the pipeline, no scandals, nothing of the sort.

People are allowed to share opinions of their previous employment and generally describe the broad outlines of their work and where they worked. This isn't a situation of working for the CIA with top-secret clearance.