Position Control Job Type and Step

In the Position Master F08101, if we manually created Positions IDs and then assign a Position ID to an Employee Master, I noticed that unless we had in the F08101 Position ID Master the Job Type and Job step, those JBCD/JBST fields were wiped out from the P0801 Organizational form as soon as we attach that Position ID to the Employee. I concluded that we have no choice but to specify the Job Type and step for a Position ID otherwise we lose that Job Type/Step data when assigning that Position ID to the employee.

Which leads to the following question #1: Do we absolutely have to associate the JBCD/JBST to a Position we create in F08101 or can we leave these two field blanks, but in a way that when assigning that Position ID to the Employee Master, the system does not erase the values from the JBCD/JBST fields only because corresponding fields on the F08101 Master were left blanks. What is the right process?