Earlier quoted context omitted.
As somebody said, "Ubuntu is Debian-based the same way milk is grass-based".
What a smarmy thing for that somebody to have said! They use the same package manager and many of the Ubuntu devs were originally Debian devs.
Many different technical decisuons.
A very different project governance.
I'm not implying that these things are bad! But different enough they undeniably are.
The fact that I can install .deb packages on my box using a port of apt does not make it Debian. (Saying this as a dedicated Debian user since 1998 and until the switch to systemd.)