Even in workplaces that is somewhat measurable it isn't.
For example as a Machinist we produce/repair items. These are assigned under work orders. With each job there is a estimated amount of time. Sometimes a 6 hour job can be done in 2, and other times the 2 hour job turns into a whole day ordeal because the job was poorly planned, parts weren't available, tooling wasn't in good shape, the previous guy just lazed about and left the workplace a mess, etc.
I happen to take a bit longer than most for a lot of jobs but that is also because I may have gotten the job done quicker then proceeded to sort out stuff which was wrong in the first place. A system that only rewards speed also damages capabilities long-term as there is no incentive to get long-term results only short term results (much like the 4 year election system...).
Other issues with this type of system is that what your boss demands of you can increase dramatically. For example if someone pounds out their job in 6 hours instead of 8 the boss sees that as those jobs now take 6 hours they can add 2 hours of work on to you. Even though it exhausts you to get it done in 6, now you have all your regular tasks plus the extra ones to do until it all adds up to 8 hours again. Only real difference is you are now burning yourself out for less.
Micromanaging is more of a thing now then it ever has been thanks to technology, cameras to watch you, ability to track time your logged on a system, etc. Going back to piecemeal work I think mainly benefits the employer long-term not the employees.