But something is being produced - it is version 2.0 of the software. This is an artifact that is then shipped to users or deployed to a server. Peter’s solution fixed the issue and did not (seemingly) create further maintenance burden, which would have taken attention away from other tasks, i.e. reduced future productivity.
I agree that metrics for programmer productivity are often useless (e.g. using lines of code is a bad idea for obvious reasons), but it seems silly to claim that the entire concept of productivity does not apply to the production of software.