It is understood that if you work by objectives, there must be a flexible schedule, even if it is within certain parameters, such as time slots for entering and leaving work, and also a minimum number of working hours, and also specific tasks to be able to achieve the objectives that are set. Although, from a business perspective, you can also take into account that if someone achieves these objectives with few hours, it will mean that this person has a great capacity for work and can contribute a lot to the organization.
But sometimes working by objectives can mean very complicated milestones to achieve within a standard working schedule, and can imply having to work many more hours without being paid, and it can also implicitly bring the problem of how the productivity of the workforce is measured, if the objectives require so many additional hours to achieve them.
And at the other extreme, there may be cases of people who work their working hours, or even more, but who do not have set goals for themselves to achieve, and this can mean that they are not sufficiently effective in their work, since they are not clear about the direction they should follow.