Logging in Across Accounts IG —-> FB

Has anyone seen this “Logging in across accounts” feature in Instagram under Settings > Accounts Center? It seems to suggest that by enabling it you can now log into your linked facebook account via instagram. When I enable it though nothing seems to happen. Perhaps it’s a feature being rolled out soon? I always thought that by allowing instagram login via facebook but not reverse, facebook was attempting to establish the facebook app’s authority over instagram. That would make this move a bit surprising. Then again, it doesn’t seem to work so I’m not really sure what this is. Any ideas? Anybody else have this feature enabled?

Pic for reference: https://imgur.com/0Ld9kOg