I'm on MIA-MXP tomorrow (Apr 25) and C space finally opened up this morning (Apr 24) around 9am MIA time. This flight was completely wide open (seatmap only 25% full in business and 7's across the board on EF).
No idea what AA is thinking on this flight
but it's obvious they're holding space on it till the last minute. There was tons of other C space open much further in advance this week on a variety of TATL flights that were way more full in business than this one.