Replying from my phone. I think the project now uses "KDE" to refer to a combination of the organisation and its developer community. The project now uses the phrase "KDE Frameworks" to refer to the libraries and frameworks for the desktop environment. Finally "KDE" seems to have been rebranded "Plasma Desktop"; however, major revisions are sometimes branded "KDE Plasma x", where x in an integer.
I suspect that "KDE Plasma" is meant to signify "Plasma, by KDE" (Eg: by the organization and greater Dev community) or maybe symbolically "community desktop".
It might alternatively be transitory branding, eg: it makes sense to keep "KDE" for people who know what it is, and add "Plasma" for the new generation who only know the DE by that name.
So I think the change is sensible, although I find it confusing that the KDE acronym seems to be in the process of being redefined. I liked the old name: Kopernikus Desktop Environment 😊