The functional difference between a change and a cancel and rebook is that a change doesn't require existing award inventory if you only want to change part of your existing itinerary, a cancel and rebook requires availability for your whole itinerary.

For AA bookings, there's likely always availability at a higher price point, so functionally cancel and rebook is always going to be available and show - it'll just charge you more miles (as is visible on your screenshot).

It's just not really a "change", per se.