Small productivity drains on minority portions of the task are not a requirement of doing the job. Software developers generally spend more time thinking than typing. Typing is not the bottleneck of the job (at least for the vast majority of roles).
Sure, of course typing is not the biggest bottleneck in software engineer job. That doesn’t mean it’s irrelevant for productivity.
Consider another example: police officers need to do a lot of typing to create reports. A fast typing officer can spend less time writing up reports, and more time responding to calls. That makes him more productive, all else being equal. Of course it would be silly to consider typing speed as a sole qualification for a job of police officer (or, for that matter, a software engineer), but it is in no way unreasonable to take it into account when hiring.
