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!