Driver,
I will add to my thought, that if management is requiring that all the Cessna checklist items are being carried over to your company checklists, and this is capturing the use of the parking brake at certain occasions, you might present the other side of the situation to them....
If your company procedures require the pilot to apply brake pressure at all times no motion is desired, and your checklist does not make any statement with respect to the use of the parking brake, you just evaded being assigned responsibility by the pilot of a errant airplane, who would surely say: "But I applied the parking brake, as the checklist said, and it still moved, it's not my fault!".
If you need more cheklist insight, PM me. Writing Flight Manual Supplements and checklists is a part of what I do, and I have some background information which might be of help to you...