Wherever you’re getting your info, it’s not a good source.
Rowling featured automobiles, trains, and modern residences in a folklore-based series full of slave economics and discrimination against Muggles. Regular tech was used to show off how wonderful (mild sarcasm from me here) child endangerment and the brutal labor of a slave class is. The books were written in a city known for its Medieval architecture when home computers and cell phones were generally unavailable to kids and young adults. Being able to message someone or see their face long-distance in real time seemed like magic.
The real-world setting already feels different today to how it did then. But that’s an Urban Fantasy series set in modern times showing modern technology. Certainly not Medieval. It’s obvious in the art and adaptations that the students typically aren’t dressed in Medieval clothes.
As for the other example: Tolkien set his Lord of the Rings’ Middle Earth in prehistory, thousands of years before the Middle Ages / Medieval period.
Our real world Middle Ages had robots, computers, skyscrapers, innovative fabrics, and medicinal studies in addition to the remnants of earlier “magic”, or spiritual practices that today’s religions and fantasy fiction pull from. They were “Dark Ages” because of how much oral traditions and long-term records were lost.
Ancient times had technology today’s peoples still trying to relearn. That includes some type of computing, energy storage, and impressive feats of manufacturing and construction that reshaped skylines, shorelines, and our bodies.
One of the reasons I like when classic fantasy and science fiction tropes are mixed, which I’ve seen done since the origins of the genre, really, is it seems more honest about how humans do things.
Many Fantasy writers deliberately simplify as much as they can. There’s a reason the supposedly complicated politics in epics tend to be built on stereotypes. But that’s not the only method already in use.
By the way, much of the history of real-world tech before the Industrial Age won’t likely pop up in chatbots that were built from badly scraped datasets. That’s because what’s been filtered out and manually screened. Just like in the Industrial Age, the best known makers and users are subjects in feminism and Queer Theory studies. Those records are disappearing fast because of destructive political situations, but it’s where to look if you feel like digging into history for inspiration.