Automatically creating a shadow account for everyone on Instagram?
Even allowing people to follow that account?
Sounds like they really wanted to push Threads out the door in a big way.
My understanding, it is reporting people who specifically elect to sign up for Threads using their Instagram account. On instagram profiles, they have been showing a badge with their Threads subscriber number that you only get when you elect to join Threads. This increases sequentially.
The highest number on the badge should give a good indication of how many Instagram users at least “claimed” their Threads account.