This reminds me the article "Now That's What I Call a Hacker" [1], where a guy left behind his automation scripts when switched companies, which revealed some extreme scripts, like:
> hangover.sh - another cron-job that is set to specific dates. Sends automated emails like "not feeling well/gonna work from home" etc. Adds a random "reason" from another predefined array of strings. Fires if there are no interactive sessions on the server at 8:45am.
I'm putting this article and what you just said together. Now I think it's reasonable to believe there are a lot of IT professionals doing this, they are just hidden, because there is no reason to share this kind of works experience, as it makes sense in the competitive side of the industry.
[1] https://www.jitbit.com/alexblog/249-now-thats-what-i-call-a-...