I think the headline could be a bit more nuanced as when I first read it I was a bit confused. Then I read the article:
"When Simpson won her world title in 2011, she ran 4:05.49 and closed in 47 and was world champion. Tonight, she closes in 45.20 in a 4:02 race and got crushed."
The point being if you take out the names of the races and the place this may have been the best race of Simpson's life from a physiological standpoint. So from a physiological standpoint this arguably is the best she's ever run.
I've added an asterisk to the headline and am linking to this thread.