I think what you are trying to say is consistency is better than inconsistency given the same amount of work. The consistent worker will be able to get items done in 5 days, but the inconsistent one will take 3 of those days, do the work, then twiddle thumbs at work for the next two days to regroup. Both are "ready" back on the start of day 1, but which one is more efficient?
One could argue that the person can make a better use of the two extra days spent working but not productive on items related to specific work items. So it may not increase productivity to the employer but it increases productivity to the employee.
If I sell you a Book for a million dollars, I make 1 million dollars. If I sell a million books for a dollar each, I make a million dollars. My Company is worth a million dollars. It makes no difference to the quality or what i am selling.
One could argue that the person can make a better use of the two extra days spent working but not productive on items related to specific work items. So it may not increase productivity to the employer but it increases productivity to the employee.