I wonder too if there was more of this before Agile. With deadline driven development you can run into situations where part of the team is stuck waiting for their teammates to finish something so they can surpass a milestone. You can only poke at the backlog so much. Boredom and being able to rationalize that you aren't really affecting the roadmap by sneaking a little extra something in makes for a lot more 'motive and opportunity' situations.
Today some auditor (like me) would fail your ITGCs because of the undocumented partition/file/change/etc (take your pick) and force you to submit a deviation to the SOC team, ask you to "review and update the Secure Design Document to reflect to the change", ask you to create a Jira and/or ServiceNow ticket, etc. etc. etc.
Oh, and you would get a red mark on your "HR P&D record" for the 'Secure Software Policy' violation.
(Shit.. I hated myself writing the above, but it's true)
In 2001 though, we would all laugh if we would have 'caught' the devs doing something cool like this!