Facebook and Instagram currently each have their own login screen — after all, even though accounts between both platforms can be connected to some degree, they’re still different logins across different platforms. The new update doesn’t change that, but it does bring a unified login experience for both apps. The new Account Center features a unified UI across both apps and doubles down on the integration that currently exists. If both accounts are linked, you can sign into Facebook using your Instagram login, and vice versa.
Perhaps the biggest improvement here, though, is the addition of a new account switcher that not only lets you switch between different Facebook/Instagram accounts on their respective apps but also across them. If you’re on Instagram, and you want to hop over to Facebook, you can do so through the account switcher. It’s arguably a quicker experience than exiting the Instagram app and opening Facebook, or vice versa if you’re the kind of person to frequently switch between both.
The new Account Center experience is currently in testing. If it does make it through as a final feature for everyone, it won’t happen for a few more months.
Source: Meta