This has been a legal requirement by the government for a while, in order to combat counterfeit money. Many tools that work with images will complain about banknotes, even printers.
Also it’s not AI based and isn’t sending your image to a server. It’s checking for certain specific anti-counterfeit details of banknotes.
I’m on .ml and have been considering making an account on another instance, but it seems like most major instances require an email. .ml did not require an email.