Okay here's
my understanding .. do NOT take this as "guidance" as I don't work for Ubuntu, then you'll not be misguided.
The "core" of "Ubuntu" is a pretty much a collection of third party software "packaged" for Ubuntu by trusted package maintainers (most of which are not "paid" by Ubuntu).
MOST of these (core) packages are common to all "*buntus".....
Packages specific to
Desktop Environments however have their own respective "teams" .. there's a team for the Ubuntu DE (who concentrate on the Unity DE packages)
https://launchpad.net/~ubuntu-desktopthese work closest with the Ubuntu management as any changes to "core" packages required by them are a priority for "Ubuntu"
there's a separate team for the Xfce DE
https://launchpad.net/~xubuntu-devthere's a separate team for the LXDE DE
https://launchpad.net/~lubuntu-devetc.
They create the packages for their own respective DE's and make sure they work with the "core" packages dictated by the "Ubuntu" team and management.
Any changes to DE specific packages required by changes to "core" packages are taken care of by the respective DE teams.
Sure they have meetings to make sure at the end of the day they mesh without conflict but they are also
semi autonomous within the larger framework.
Now back to your original question....
They have separate ISO's with their own websites because
a) it makes sense that if you want info about *buntu with LXDE (Lubuntu) you have a separate site for that, maintained by the people that develop that DE.
b) it also makes the ISO's smaller than including ALL DE's on one ISO .. and the main Ubuntu site less confusing (all about *buntu with Unity, and not say - here's how to access the printer util in Unity, and here's how if you're running LXDE, and here's how if you're running Xfce, and here's how if you're running KDE.....).
c) It makes "support" easier .. if someone on the forum says "I'm running Xubuntu 16.04" you know the starting point and their system likely isn't clogged full of Qt libs/etc.
And finally, let me also be blunt ..
you're wrong, and if you're quoting him so is Simon Quigley (whoever he is) .. there are no Ubuntu "community editions" just "official flavours" (who yes attempt to semi-sync release dates
WHERE POSSIBLE)
https://www.ubuntu.com/about/about-ubuntu/flavoursand unofficial spin-offs who are not in the "core" input/feedback loop.
This is my last posting on this topic .. if you have further questions on how the Canonical/Ubuntu organisation works ask them .. only they can guide/misguide you, anything from me is/was simply an attempt to answer your question
FROM MY UNDERSTANDING .. take it or leave it, but don't consider it official Ubuntu "guidance", I have ZERO connection to them.
