What you are referring to is the Angel Watch program. Basically if you are a registrant or obliged to register, whether you notify them or not per the 21 day rule, they will notify your destination country via a Green Letter.
Given the presence of the Angel Watch program I question WHY IML was even thought to be necessary. Instead, now ANYONE who ever asks for your passport – specifically those who never had a right to know you are an RSO (banks, hotels, etc) – will know. That was the real reason for it – to expand the scope of the persecution.