Does a user have to opt in to ATT via both the Facebook and Instagram apps?

Facebook has communicated that for a user to be considered opted-in for device level ad data, the user must opt in to ATT on both Facebook and Instagram (if both are installed on the device).

This means if the user has both the Facebook and Instagram apps installed, and opts in via ATT with the Facebook app, but not the Instagram app, Facebook will consider that user opted out, and will not respond to device-level conversion requests via the MMP API endpoint.