Like with Mattel who makes, markets, and distributes Hot Wheels and Matchbox.
I was waiting for you to get there.
Mattel is easy, if they don't have their own factory(s), then they are definitely big enough around the world to do their own distributing under their own name. They are not reliant on a third party for distribution...you order from Mattel and take possession of goods by the case. We know Mattel is the designer, if not maker outright then they are the contractor that orders production, and they receive and distribute, and their products are sold under their controlled trade names and trade dress. Easy peesy.
Let's make it a little more complicated. Johnny Lightning...as it is now under Round 2. TOMY still holds control of the physical tooling that they acquired when they bought Learning Curve, which included Ertl, Racing Champions and Johnny Lightning. Since TOMY also hold Tomica, a lot of the diecast was, to be polite, redundant. There were other "brands" in the mix as well, not important to collectors of diecast but certainly important to TOMY, the Thomas Train franchise in particular. From any business 101 text a person can find that one way to eliminate competition is to buy them out and close them down. And that was a concern among fans of JL when TOMY bought, and a few years later when things didn't go as TOMY had hoped, they did indeed close JL. After which, Tom Lowe was able to purchase the rights from TOMY to continue using the models and tools his former company Playing Mantis created, as well as some of the RC and Ertl tools, and the rights to use JL and RC trade names but not Ertl - TOMY has kept the rights to Ertl and continues to use it to sell agricultural related diecast. This is why we were able to find mixes of Ertl, Tomica and JL models on the same shelves in Tractor Supply, Rural King and other ag related businesses that sold ag toys. Back to present, Tom Lowe and company design a model, send the specs (like the build sheet I showed today in the other thread) to the factory in China and contract how many and how they should be packaged, which when the contracted run is completed it is shipped to Round 2 (I think they are still outside of Chicago), and they distribute to their customers from there...I think. There are other possibilities, cases could be shipped directly to customers (someone the size of WalMart or when we had TrU before they closed, possibly Target). I have no doubt some companies like Round 2 might use a third party distributor, so it is not out of the question, but since Round 2 does maintain their own warehouse (PM Vault still sells NOS Johnnys on the 'bay), I would be inclined to think they do their own distributing.
Some of this is about who puts the upfront money to have the contracted run made. One way is to contact the maker, and buy whatever they have already designed so there is no custom work other than maybe packaging...and why you can find essentially the same model packaged and sold under different trade names (Maisto comes to mind here). Alternately one can contact the maker and custom order a specific model or models, with custom decorations, in the requested quantities, and have them shipped wherever you want. In either case, the distributor might be the one here who puts the money up front and receives the goods wholesale to sell wholesale to retailers to sell to the public. In our example here, it is very possible Greenbriar put up the money and contracted the run to be delivered to them for distribution, and clearly a portion or maybe the whole contracted run was sold to Dollar Tree distributors who sent the cases of product out to each of their stores for sale. How the Canadian distributor fits in isn't clear, they may be a subsidiary of Greenbriar, they may only be a limited partner with Greenbriar, they may have put up the money for the contracted run and Greenbriar is subordinate...we will never know. But they perform the same function in Canada, distributing to whatever company(s) it is they are dealing with to final sale to the consumer. Ja-Ru and MarzKarz filled the same role of distributor for Summer products years ago, and Imperial is still in business today and I know they were around in the 1970s.