Do material requirements from Job count as demand for MRP or requisitions?
Yes, they can. You need to ensure two fields are set on the Job to allow the MRP to pick up the demand.
The first is the Job Status field must be set to OPEN.
The second is you must have Apply Usage Link set to TRUE (toggled on)
With these two fields set any Item lines in your Job Planning Lines will be picked up as Demand in your MRP calculation.
Be sure you have your Location Code set on the Job Planning Line so the demand is in the proper Location.
P.S. You can set the Apply Usage Link to default to on in the Jobs Setup.