Not surprised at all. Her 100 times indicated that her speed is back to its old form. Which means her 200 should be back as well.
In addition she got some good speed endurance from 400 training last year. So she built her base then added speed.
Perfectly sound multi-year training, and here is the result. No surprise at all.
I would be surprised if she doesn't PR again before or at the Olympics. 21.5 is not a stretch for her. The next few years will probably be her fastest. I really hope she stays around to her mid-30's, she is so good for the sport. Another 9-10 years of her as the face of the women's team would be great.