AA gets the information around the same time the media does - when the Argentine government (ANAC, the body in charge of civil aviation, after consulting with Ministry of Health and others) grants its approval. Sometimes the approvals come in bit by bit rather than all at once - meaning until it’s actually declined, airlines will continue to sell it.
In the small print flights are often sold “subject to governmental approval” or similar in the terms of carriage you agree to when buying a ticket. It is common practice industry and worldwide for airlines to sell seats that are not guaranteed to operate, but are hopeful of getting permission from the relevant authorities to operate as scheduled. For this reason last year we saw Argentina completely ban all scheduled commercial international flights because so many people were stranded and the government argued that capacity into Argentina needed to be reduced for sanitary reasons. Now that ban is gone, airlines are free to sell what they want but it’s buyer beware since approvals are revised every few weeks by the Argentine government who is about as predicable and dependable as ... Argentina ;-)
