I brought it up with alan, but she said that she has no control over that since it's all under Avex.
But if you change to Spotify Japan, all of her Japanese songs are on there (except the new tracks of JAPAN PREMIUM BEST for some reason)
You just need a Japan VPN and change your location to Japan in Spotify's settings.
Edit: I also made an alan Discord server. It's easier to update her day-to-day since she's very active on Chinese social media. She reveals a lot about what she's working on. I'm also putting the album lyrics translation of "Thoughts of a Decade" on the server for now.
https://discord.gg/XpPsHP