If by reloading equipment you mean powder and primers, you are right, but they do allow sellers to sell bullets, cases, dies etc. They also sell barrels, mags, clips and more. eBay is a good source for all that stuff.They will not accept arms for sale or reloading components but will this sign.
I would guess that there would be some liability on eBay's part if a seller shipped gunpowder without following regulations, or if someone sold a gun to a buyer who was not qualified, by law, to purchase one. I think that's what places like Gunbroker are for. Personally, I wouldn't want to buy a gun like that, but that's me. I prefer to put my hands on it before buying.