This is likely done as part of twitch extremely slow rollout of restricting giving out personal data. (GDPR)
They have been doing similar stuff with follower-lists and asking third-party services to remove their chatlogs.
And i dont buy the argument that it was to hide bots:
Twitch has removed the "Following Since" date from view for all users.
Streamers and Moderators can still see Account Created and Following Since information locally on their channel.
