GSP FF Multiple assignment with same grade, GSP on both the assignments to be cumulative

GSP Question

Hi General GSP experts we have the below scenario and I would your like to get your inputs. We are trying to build a fast formula that add the total hours for all assignments for an employee. However, our internal tech team has informed us that for multiple assignment with same grade, Grade step progression on both the assignments to be cumulative-Cannot be handled in automated process and has to be done manually”.

 We would like to know if this is a common requirement?

Have you implemented in the past using fast formula? So, it is possible to build a FF that calculates the cumulative hours for multiple assignments with the same grade.