I am purchasing new load cells for a tensile testing machine and am finding that the load cell supplier requires a technician to come and complete a force verification for traceability purposes. We calibrate our own load cells in the tensile machines and thus I believe this verification is something not necessary to have the supplier's technician do. However, the supplier requires this to sell the load cells. Is there a reason for this if we complete this in house ourselves per ASTM E4? Am I missing something or is this a sales tactic?