I have seen many photos. What is the principle of out-of-focus imaging as a rotating vortex? Is it the characteristics of the lens?

Yes, each kind of lens and each brand have different characteristics.

Just from the pure Jiao Wai blur, some colors are directly diffused, and some will blend with each other.

Go to the portrait pages of Green Shadow Wuji and Hummingbird, and you will know the Jiao Wai blur difference of various brand lenses.

Attached is a picture taken with Minolta 80-200apo2.8 lens (not provided). You can take a closer look. I feel the wind shaking where the grass meets the red and green cherry blossoms, and there are black branches behind the characters. The whole looks like it was fused with a watercolor pen.