Incorrect, the standard links are not churnable with in 18 months.
i did not realize there were special links, but I just googled it now and the offer is still available, and it had the 18 month language on the top of the page:
Earn 75,000 American Airlines AAdvantageŽ bonus miles after making $7,500 in purchases in the first 3 months of account opening
American Airlines AAdvantageŽ bonus miles not available if you have had a CitiŽ/AAdvantageŽ Executive World EliteTM MasterCardŽ opened or closed in the past 18 months.