He does however claim he'd learned of questionable/unethical hiring practices as part of a "secret" diversity hiring meeting he'd been invited to attend, and this is what prompted the memo in the first place.

What I inferred from this, is that he learned that at least in some cases, there's aspects to Google's diversity hiring that they'd rather people not know about.

Now I don't know if this is false, true, or true within a small subset of Google; but his claim of the secret meeting does change the narrative somewhat in his favour.

Not unless he can provide some evidence for it.

I mean yes, one needs to be skeptical of "secret meetings". But it doesn't actually change his argument, it just reduces the validity of certain claims of subtext that he believes his female coworkers are inferior.

Basically, you're asking for evidence so that he can prove himself plausibly innocent of a crime that there's no evidence for in the first place.

Is there a good resource for what Google's diversity efforts actually include?