If you want true and well functioning rolling you go either Arch, OpenSUSE Tumbleweed or something that rolls slower like OpenMandriva ROME which is simpler than let’s say OpenSUSE Slowroll. Personally, Arch is by far the best (because it’s K.I.S.S.), then I’d pick OMV ROME most probably, and both are purely community-based, no corp overlords with their agendas and whatnot.
I find that humorous. If by “rolls slower” they mean, releases updates slower, then they fail to address that many “rolling” releases do not publish some software at the current version. Arch may not be ruled by oligarch money specifically, but they are the basis of other Arch based distros and script front ends like Arco. The AUR exists because they have some software they will not touch, or is too new for them to include in a release.
Fedora and OpenSuSE both have fiscal responsibilities to their parent companies, foundations, and organizations first. As such, they hold back or backport fixes for features they lost when adding new ones all the time in their “rolling” releases. This is why wayland has not become more reliable, stable, and functional.
Coming back to the core statement, nothing stops a user from turning Neon or Kubuntu into the other in terms of versions. It’s about whether they want to just use it as is, or take advantage of the flexibility of building their own software. The base systems are the same, with Neon just having the newer version of Plasma. Since Vivaldi also has fiscal responsibilities, they are going to hold their library versions back to a more LTS like experience because they want their software to work for people that just want to use it and do not build their own software. It’s a catch-22.