"I'm a bit dizzy and I've been coughing blood but I feel fine."—This sounds like the sort of dumb thing I might say to my own doctor. XD
@I_need_a_break:
While your point is well-made, fountain pens are a pretty mild transgression by the standards of these things. They're at least distinctly pre-industrial-revolution and don't require any advanced metallurgy or manufacturing techniques or some-such, and there's evidence da Vinci may have made a working one (so, renaissance) which is enough to consider that royalty might have gotten one. Given a little leeway for things being developed sooner or later in some alternate universe, it's not inconceivable.
I mean, almost all of these stories are de-facto set, by all appearances, in renaissance or later periods. Medieval stuff just doesn't have enough frills in the commoner's dresses in town, the confectionery isn't up to par for a shoujo-y manga,
there's not even tea. The moment you've introduced tea in your story it's not really medieval Europe you're talking about anymore.
Not that any of these are claiming to be historically accurate, of course. The question seems to be more whether "medieval" is even an apt description, in even the broadest of terms.
I have always believed the crux of the matter was that, "medieval" is a word that also has informal use as just "old-timey primitive stuff before industrialisation", whereas "renaissance" and later periods
only refer to specific times in Earth-history, which seem weird to many of us to use when describing a fantasy world. (Though it could come down to some other totally inaccurate thinking reinforced over the years, too, like: "Renaissance means muskets; medieval means no gunpowder")
The only one of these I've read that actually felt convincingly medieval (dirty, drab, gritty, feudal, chauvinistic and horrific) is
Emperor and the female knight and I think it itself demonstrates why we don't usually do that (even if I do quite like the series).
Woah, I somehow just kept talking for way too long there, sorry. XD