Tamriel's civilization is older than the real world isn't it? I'd hardly expect all technology to be completely stagnant after hundreds and even thousands of years.
No, but the best we can do I'd think is use other items for a comparative level. Or maybe even the windmill design would indicate at time period from which we could see similar windmills in our time. I think the idea of Tamriel's tech level to its civilizations length is magic has stagnated a lot of its technology. Why learn advanced surgery when the local priest can wave his hands and cure any hurt, disease or other ailment. And its not like a D&D world where only the special few can and do learn magic, virtually everyone can learn magic and most probably know at least no a little bit. Given that virtually all the other tech which seems to come form roughly the same time period in our world why would windmills be leaps ahead in tech comparatively. So from a time period of horses, swords, bows, with no electricity, fancy plumbing, gas or steam powered devices would a windmill from a similar tech level or time frame rotate?
It might, windmills are not exactly part of my history lessons.