Yes, yes it is; and here’s proof why
Given the fact that winter tires have a soft compound — and high adaptability to low temperatures — it might be normal to see them as summer tires with but higher wear. Don’t.
The YouTuber who teaches us engineering one clip at a time explains in one of his videos why wearing winter tires during the summer is a stupid — and, more important, dangerous — idea.
Although the compound on the winter tire’s tread is softer, it can’t cope well with high temperatures, so, under hard braking, the winter tire will crumble on the asphalt like a cheese roll. For safety reasons primarily, in the dry season stick with the summer tires.
Furthermore, the winter tire’s tread design — with its multitude of grooves that create sticky edges — might not be helpful when encountering an adherent surface as dry tarmac. It’s worth watching the clip, as it has not only strong, well-documented arguments but also real-life testing.