I thought a lot of these restrictions stem from the manufacturers/government and aren't Amazon's decision. That would be flooding the Canadian market with cheaper goods than are available here and there would be a huge legal battle with that. If you can start ordering this stuff on Amazon, then it means they lifted the restriction and you will be able to order elsewhere too (ie bestbuy.com).
Checking your second link... it appears most of the products that are available are only the usual products allowed in the canadian market... most of the good stuff still isn't allowed. Oh well, good to at least have another competitor for the products we have here already.
Surprised you can order a SB5101 cable modem though... I thought companies in Canada no longer register them unless purchased directly from them?