When writing a cadenza for the pianist who taught you about stride, what do you expect to find in it?
Repeated notes, sure. Because that happened earlier. But …
Oh, what happens just before this? Duh, crescendo in the orchestra and sharp cutoff. It's another way I know how to end a section.
By the way — WTF is WTF? It's where, 40 minutes into the concerto, the piece starts again. That's what happens after Amy turned off the camera.