Other than one poster that was evidently not let in on arrival at MIA pre-pandemic (and who ironically keeps asking this same question about MIA over and over) I'm not aware of any other data points of these "infamous dragons" not allowing FFD on arrival.
FFD access has been thoroughly discussed in the master threads:
Guide to AA Flagship First Dining Qualifications, Access & Related
Flagship Lounges and Flagship First Dining to start reopening September 2021