Yes, that's a different matter. If the maker, Leupold/Redfield didn't get their product licensed for export it would be illegal for them or anyone else to export them, and no export permits would be issued. Since they did get them licensed, they can get the necessary U.S. government permits to export them to their Canadian distributor, Korth, but as far as that goes, the U.S. government permits for export could be applied for by any other wholesaler/retailer/private owner to sell them to Korth or anyone else in Candada. But Leupold or any other manufacturer is free to make it a condition of selling to U.S. customers that they not re-sell/export to somewhere like Canada where the maker has a granted exclusive distribution rights to a company like Korth. That is a matter of private contractual obligations, not something the U.S. government would enforce by not granting the export permits.
It's not always BS. Some dealers would not consider selling optics to Canadian customers even it the manufacturer had licensed their products for export and not placed any restrictive contract terms on re-selling, because they think learning the export permits just isn't worth the trouble for the volume of potential sales to Canadians. Some of them may be wrong about that sometimes, but it's their business.
I'm sorry, how is it a different matter? Op stated "It turns out most scope manufactures have put a stop to Canadians buying scopes in the USA.". Which is to say, he tried to buy a Leupold from the US but they couldn't ship it to him because of manufacturer sales restrictions due to distributor agreements. I didn't see any mention about the US government.