Thunder saving credentials even after reinstall?

Thank you for the wonderful app. I have one issue though. Since I found it out in Play Store, I uninstalled the alpha version and installed the one on Play Store. It didn't let me sign in saying my credentials are wrong. So I installed V0.2.1-alpha.4+13. And guess what? When I went to login, it said it's already logged in to my lemmy.ml account. Why did this happen?