It depends. A gifted and creative programmer may be able to accomplish in 3 hours what takes an average programmer 10, or by coming up with a creative approach to a problem, may be able to accomplish in 3 hours what an average programmer simply cannot do at all.
So while a manager may dislike that they perceive someone to be slacking off, it doesn't necessarily mean the person isn't providing a lot of value to the company. Value produced and hours worked are fairly loosely correlated for knowledge workers.
If you were running a startup, would you rather have 12 focused hours per day from a mediocre programmer or 2 from Linus Torvalds?
So while a manager may dislike that they perceive someone to be slacking off, it doesn't necessarily mean the person isn't providing a lot of value to the company. Value produced and hours worked are fairly loosely correlated for knowledge workers.
If you were running a startup, would you rather have 12 focused hours per day from a mediocre programmer or 2 from Linus Torvalds?