As far as jpop goes, a LOT of their JP catalogue didn't make it over, so that's why you're probably seeing a big shift towards other genres. Also, a lot of their JP stuff is in curated playlists that non-JP listeners can't access. For example, the intro to Koda Kumi playlist has one song in it. Japan's been cold on iTunes, so it's not much of a surprise.
Though to me its weird that following the JPop Curator gives me access to a bunch of playlists that never get promoted in For You. And that reminds me how the Apple Music J-Pop Editor is totally buried whereas you'd think it would appear on the same place where all the other editors pages would.
And that brings another weird thing in terms of playlists. I see playlists full of stuff thats in my Apple Music iCloud library but they are all greyed out in the Apple Music playlists. Certainly I understand why (the tracks aren't licensed for Apple Music in my country) but you'd think it would look at what's in my local library too.