I thought the store at Japan was operated by Mitsukoshi? That might be why not but it should be noted that much of what you can buy at Tokyo
Disneyland and Tokyo Disneysea is not even sold outside of the parks even. And not even at the other park. You are able to buy through some personal shoppers at least. The Hong Kong merch can be found at HKG Airport which is nice at least if you miss something in the park. In Tokyo, you are out of luck without going back into the park. The Tokyo
Disney store has a few things only sold there. At least when I visited in April at the Shibuya store.
[Will add that we bought Duffy items at HKG Airport and wanted to buy Duffy items from Tokyo Disneysea but they are not sold outside the park at all. Got a few of the spring plush and a bigger Olu with a free outfit as part of a promo at the HKG Airport disney store.]