Travelling YYZ-TPE, 2 J seats started to appear about 2 week before departure. Picked them up 1 week later. Availability turned to zero right after. A few hours later, 2 more J award seats became available. And for my connecting flight TPE - KIX, zero J until 1 week before departure. This was for departure last a few days ago.
When I first looked 3 months ago, there was nothing for departure in the same period.
So it appears they actively and dynamically manage the award inventory when they have unsold seats. BTW J cabins were full when I was on those flights.