Well, I did say "middle- to low-performers" above.
But regardless, I disagree with your premise. Software engineering, as a profession, is based largely on trust. This isn't a factory where you have to solder a set number of devices to meet your target numbers. This isn't an animation studio where you have to animate a certain number of director-approved frames ("footage") a week in order to meet your performance expectations.
In our field, the engineer largely decides on their own how much time a task should take, and the manager hopefully trusts their estimate. The *assumption* (and it's not spelled out in your employment contract because we're supposed to be professionals) is that a day of effort means a "full day" of 7-9 hours (or whatever, the precise number isn't the point).
So if I, as a manager, ask you, the developer, how long this feature will take to build out, and you tell me "5 days", well I think it's fair for me to expect you meant 5 "full" days. And because I trust you, I'm not going to look over your shoulder or try to pre-solve the problem you're working on -- I will ideally just trust that it takes you 5 days. And because I think highly of you, I will trust that the work takes a dedicated and fast-working developer 5 days to finish, and that's that.
If I find out that all along, you really were working only an hour a day, then I think it's fair for me to say: "What the actual fuck, you tell me these tasks require a week of effort but they really could have been done in one day, and the project could have been moving 5x faster than it has been."
But... the other option, I suppose, is for managers to decide by themselves how long each feature and bugfix should take, and not ask the developers or take their feedback, and then the manager can evaluate the developers' performance based on that. As a manager, I'll look at a task and say "I want this done in 1 day" and when you tell me "That's not possible, it will take at least a week" I'll just say "Too bad -- get to work". We don't want that.... do we?
>This isn't a factory where you have to solder a set number of devices to meet your target numbers. This isn't an animation studio where you have to animate a certain number of director-approved frames ("footage") a week in order to meet your performance expectations.