I imagine a lot of the reason they mix vendirs products together has to do with logistics. If seller A sends 100 units of product X to the East Coast and seller

I imagine a lot of the reason they mix vendirs products together has to do with logistics. If seller A sends 100 units of product X to the East Coast and seller B 100 units of product X to the West Coast it has to be immeasurably easier to lump them together (not physically but electronically) then distribute this 200 units out to all their warehouses for faster shipping. It makes a lot of sense if everyone's on the up and up. That way you ship 20 units from Vendor A to NJ to cover the NYC metropolitan region for both vendor A and B.