Yes, Intro of and why not?
Take the medieval romances that feature Alexander the Great soaring heavenwards in a flying machine and exploring the depths of the ocean in his proto-submarine. Or that of the famous medieval traveller, Sir John Mandeville, who tells of marvellous, automated golden birds that beat their wings at the table of the Great Chan.
Like those of more modern science fictions, medieval writers tempered this sense of wonder with scepticism and rational inquiry. Geoffrey Chaucer describes the procedures and instruments of alchemy (an early form of chemistry) in such precise terms that it is tempting to think that the author must have had some experience of the practice.
Yet his Canon’s Yeoman’s Tale also displays a lively distrust of fraudulent alchemists, sending up their pseudo-science while imagining and dramatising its harmful effects in the world.James Paz and Carl Kears, “Science fiction was around in medieval times – here’s what it looked like” at MercatorNet
Perhaps the idea shouldn’t be as surprising as it sounds. Most medieval literature was fantasy of one kind or another—King Arthur, the Divine Comedy, the Arabian Nights in the Islamic world, etc. So why not science fantasy?
The “realist” tradition in fiction was a comparative latecomer, maybe starting in the 17th century.
It’s not that people didn’t know the difference; it’s more that if you admitted it was fiction anyway, you were expected to take liberties of all kinds. Otherwise, why not just write chronicles?
See also: Was Isaac Newton (1642-1727) a bad scientist because he believed the world ends in 2060?