That's the long and short of it - Hasbro has some kind of master license to produce and sell toys worldwide at the moment, and they don't want companies like Max Factory, Tamashii, Kaiyodo, etc pissing in their pond by being able to distribute their figures in the West, or even sell them online from the point of origin. Hot Toys, Kotobukiya, Mezco, etc seem to be able to get around this by producing figures in a different style, scale or medium. Most likely the other companies were only able to acquire a license extending to the Far East and South East Asia as a result. Strangely enough, Medicom seem to be able to get around it, some of their Mafex figures like the premium Amazing Spider-Man 2 package were distributed by Diamond. In summary - it's a giant clusterfudge that probably nobody but the companies involved fully understands.
Expect this kind of thing to get far worse if the TPP/TPIP passes into law, at that point there'll be nothing to stop a company like Hasbro demanding that anything imported from a foreign country - even privately - that infringes their license be destroyed by customs (and no, you won't be reimbursed).
That said, I have to wonder if Hasbro will be able to keep this up for much longer. Their original deals with Marvel and Lucasfilm were inked before the Disney buyout, and prior to that they'd ensured that absolutely no-one worldwide could compete with them. Once Disney took the helm they started handing out the licenses to other companies like a Pez dispenser spitting out candies. Be interesting to see what happens when the next contract renewal period rolls around.