I don't know exactly how much time was left, or how field position compared to the ISU game, but Iowa did it last year at tOSU with the Rose Bowl on the line. We had the momentum, but went conservative, took it to OT and then lost.
Granted, we were playing with a freshman making his first start, so maybe the thought was "what if we turn it over?" That would be slightly different from your case with Arnaud at QB. Still, if he had been aggressive and Arnaud had thrown a pick, or somebody had fumbled, then you'd have questions about why Rhoads didn't play for OT.