At the link, there is an excerpt from the Follies in Concert documentary showing us Stritch in rehearsal. A bit further is the the beginning of "Broadway Baby" at the opening-night performance.
She certainly is not doing it quickly in the rehearsal clip, although admittedly she is simply trying to get the notes. Still, I would bet that she never did it in rehearsal faster than the basic tempo we hear there. If she went perhaps a bit slower still in performance, given the audience response, how could she not?