It is a 100% true anecdote at any number of businesses. It's philosophically enlightening in a way and related to an increasingly profound adage of "Purpose of the system is what it does" (which can be applied to IT and political and social and school and other systems through various lenses).
There are any number of systems out there which are "self documenting" in a weirder sense that what they do is what the rules are, rather than other way around. There's no external document or business process ruleset that describes what they do at the level of detail and accuracy that code does. There are a myriad edge cases built in which are important and relevant and likely still true (until somebody actively decides to change some rules) but not well documented or understood. I'm working on a government payroll system and it is mind.boggingly more complex than ever I could have possibly imagined and it still blows my mind every day. We have tens of thousands of time & labour rules due to hundred unions making thousands of negotiations over decades, on top of complex baseline payroll and taxation rules across governments and provinces and levels.
Attempts to rewrite such a software almost always, almost inevitably, take much longer and cost much more not just because of technical and architectural challenges, but because of, well, hubris - assumption that just because we can migrate webserver code across platforms, we can migrate a payroll system across platforms as well. Turns out one is orders of magnitude more complex than the other, we are just not used to thinking that way :).