I know nothing of blu-ray region codes, so I don’t have a helpful answer for you, unfortunately. I feel your pain, though. The person who invented the concept of region codes should be sent to a special hell where their genitalia is region 1 and everyone else’s is region 2.
I am not sure how you confirmed that these particular discs have Japanese audio and subtitles, but I will guess that you had them initially shipped to a friend in Japan who checked it on their equipment and then forwarded the discs to you. (The product listing page for Season VIII blu-ray discs that I found on Amazon Japan only listed them as being subtitled and dubbed, not specifying what languages, although logic demands that Japanese be one of the choices.)
If you did have a friend check them on their equipment in Japan, then as a way-out, off-the-wall totally unlikely possibility, I wonder if the Japanese audio came through on their setup as the secondary audio program, and if the subtitles were actually produced by the Japanese TV’s closed-captioning feature? While I guess I am reaching with the SAP angle, it seems entirely possible that someone could have spaced on whether they were using their TV’s built-in CC feature and not the disc’s subtitles.
So you might try your TV’s SAP feature.
Since the discs are from Amazon Japan, it seems very unlikely that they are actually bootleg copies that just didn’t have the Japanese audio and tracks copied to them or something.
The only other suggestion I could make, especially if you are in the habit of watching Japanese discs, is maybe to buy a blu-ray player from Amazon Japan. (Amazon Japan might not be willing to ship electronics out of the country, so you may have someone else ship it.) You might need a transformer, but it is also very possible that the unit might be designed for U.S. voltage as well. At least Japan is an NTSC country, so you don’t need to worry about that.
In for a penny, in for a pound, and all that. Good luck … it is a puzzlement.