Tumbleweed includes the YaST package manager with all the repository priority settings that make sense in Leap, but the TW documentation tells you not to use it.
You can run zypper up which is a standard updating method in Leap, but the TW documentation tells you not to do that. More than half the zypper options make no sense in TW.
That’s the stuff I mean by “derivative”. They built on a Leap base and modified it into a rolling release.
If it was truly designed as a new, independent rolling release distro, they’d have taken those things out, packaged a different version of zypper or at least a different manpage.