It looks like it takes a while for a flight to be "deleted" from the reservation system schedule, so when one it's cancelled the first action is to inhibit bookings by showing zero availability. When this is done, ITN will show the flight with the availability of zero, while AA.com will not show the flight at all as it's built to omit any sold-out flight from the list it offers you (a design "feature" I completely don't agree with). The flight will usually disappear completely from the schedule within a week.

So what you're seeing is normal behavior. As far as textual information on AA.com not being internally consistent or updated, well, that's normal as well!