That's a story invented years after the fact without historical basis. The actual conversations amongst Debian developers went rather differently.
* https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=444678
* https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=659891
* https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=659853
And that's why we now have BOTH /etc/debian_version AND /etc/os-release. Systemd didn't lead to debian getting rid of the former. So now, not only do you have people writing code that behaves differently (or, more likely, breaks) on different OS versions, it has two different files that it will look at for this.
I wonder how long it'll be before the contents of that file start resembling a user-agent string, complete with "Ubuntu-16.10/Compatible"
Fictional Debian dev B: "That's how we've always done it. Plus if we touch it it might break some guy's script."
It may not be exactly cargo culting, but at least an adjacent concept.