I was told the same thing back at the end of July when I rebooked my September travel to March, 2022 and with the last flight of my 2019 AONE3 now being on March 28, 2022. FWIW, this corresponds to expiry date listed under Travel Vouchers on this AA web page. I check here periodically to see if it's been extended as I'd prefer to do fall 2022 travel. If the expiry date isn't extended and F routes haven't resumed by March, I'll cancel my remaining 13 segments for a pro-rated refund.