For example, this employee who is supposedly spending 1/6th of their time on your job. If you say tried to capitalize their time such that you now have 6/6ths on your tasks, would the employee even accept this arragement themselves? You are effectively giving them 1/6th the pay for the same full time day of work they do anyhow. Squeezing this employee is not going to see you get more work out of them. It is going to see them leave your company and replace that job with another, leaving you shortstaffed and having to invest in vetting candidates and onboarding. Now you ask how much you get out of an employee you put the squeeze on given that this will lead to turnover and an overall loss of that full time work being done as you suffer through a period of short staffing.