That is the stated reason but we all know that is not the real reason. If they added an ascii art of a dinosaur or a message on another topic to that internal security tool, they wouldn't have been fired, probably not even a slap on the wrist, at most an annoyed "take that off" request.

> we all know that is not the real reason

No, that is not true. Some of us take security seriously.

Can you contextualize who you are, so that I can better understand “us”? You mention seriousness as an absolute virtue, but if it fires people for a harmless, easily correctable mistake in an internal tool, it is just misguided and an excuse especially if it “happens” to serve some ulterior motive.

It's not harmless. Google is very concerned about internal security, and putting irrelevant messages in security notifications makes them more likely to be ignored in the future. Your ASCII dinosaur hypothetical is a good way to think about it, and I wouldn't be surprised or outraged if that also resulted in the offender being fired.

If that was the point, then why was the other bit included in such obvious service to the "point"?

Security is a broad topic and can include avoiding legal liabilities.