Earlier quoted context omitted.
This really came with kde5. I get why they started using the name "plasma desktop". It's almost completely different thing from kde4. Whatever options / expectations people had after kde4 and earlier, they just shouldn't apply.
AFAIK they call it Plasma (just Plasma, not Plasma Desktop) because that is now the name for what was previously called KDE and KDE now is the name of the community and project that acts as an umbrella for various other projects, including Plasma but also applications such as Krita, KDevelop, Amarok, etc. The desktop environment isn't officially called KDE anymore, it is Plasma.
It's weird seeing a KDE product without a single K in its name.