Seems unsurprising to me. If you, as a company, want ironclad confidentiality from people after they leave, that wouldn't be free or automatic. None of what was shared seems to qualify as a trade secret, which would have some protection.
I've never worked somewhere that didn't have me sign some kind of broad NDA-esque clause saying I wouldn't share proprietary or non-public info for a certain period after release (imo, completely reasonably). This blog post is literally nothing BUT non-public proprietary info. Like the parent I'm really surprised the blog author feels comfortable sharing all this. Even if it ended up being technically legal, I have to imagine this kind of thing is extremely frowned upon.
