One of my friends who works in a recordshop explained me the system.
We only do re-orders if there is need for the record. If there are any records left they go back to the distributor. Better give it back in 2 months than keeping it 6 months... Or else the distribution doesn't have a chance to sell it to others because the record is dated.
You see when the shop has a right to send back records, you will encourage us to order more records, because the risk is lower till none. If all the records are sold, the distribution can only be glad that it did so.
The backstock in the shop is all stuff that we cannot send back. Or that we just buyed from known labels like Drumcode or Green Velvet for example.
Well this explanation sounded plausible to me.