I've return/rebuy 1 other thing at different Home Depot before and I haven't heard of this "policy". Is this store specific or corporate policy??
The only line I've ever got when calling corporate about matters like these is, "It's Home Depot's official policy is to leave it up to the store manager to come up with their own store policy". Although it's been a while since I've called in (last summer), I imagine it hasn't changed since then.
Personally, I like to limit my face time with store managers/assistant managers to instances when no other option exists. That way when I find a pallet of penny compressors in the overhead, I'm not dealing with a store manager that remembers me as the guy who recently argued with him about doing a return/rebuy.
In that regard, if a store is giving me guff about doing a r/r, I just accept it and drive to another store or come back later when someone else is working.