I don't like to think of them as "beginner" desktops.
if nothing else, I would think of them as:
"consumer" grade ( for folks with intentions only on 'using" a computer for generic purposes )
an "industry" grade ( for folks who need to make an OS and software perform differently than a "consumer" would need to)
I know of people who 'use" Windows and apple OS's for many years who never ever delve into "advanced" uses and functions on the computer because there is no compulsion or need for them to do so.
they develop a solid familiarity with the OS and can find their way around easily and troubleshoot "common" errors handily, but neither attempt or care to problem solve at what you might call and 'advanced' user level.
I think one of the primary "image" problems with Linux is that the dominant user base still uses hierarchical identifiers or labeling to describe users.
It's likely one of the biggest contributors to the myth that Linux users, especially "gurus" are egotistical and condescending.( aka "snobs)
mind you, I said" myth" because the vast majority of Linux users aren't that way, but there are a few folks that have influenced terminology enough to give that impression by making it part of the common lexicon of Linux interaction.
for terms of comparison, one could call Windows a "beginner' OS. it offers the same type of interaction and user experience.
no, I don't think beginner and advanced are appropriate terms to use to describe the type of interaction and user experience one finds when using various Linux Distros.
I do prefer "consumer" and "industry" much better.