It can be confusing. Took me a while to understand it once I moved to Missouri. Where I grew up in Florida the lakes don't stratify much if at all because they are clear and shallower. It takes a pretty good temperature difference before it stratifies. Wind energy is amazingly powerful on water and the longer the open stretch of water the more effect it has. A 10 mph wind a half mile from the shoreline creates small waves. That same 10 mph wind blowing over 5 miles of open water can create much larger waves. Wave action is much more than surface disturbance. It can create significant currents below the surface as well and that keeps the lake mixed except when great temperature differences occur. Namely middle of summer and deep winter. With last year's mild winter we may not have stratified at all.