Exactly as I thought. Sunday evenings/Monday mornings, and Friday afternoons are the peak business travel periods of the week: heading out for a week on the road, and heading home at the end of that week.
I suspect this is a combination of two things: heavy advance bookings for those very reasons, and an anticipation by AC that there will also be a lot of last minute bookings or flight changes to be accommodated from full fare flyers. Thus they are keeping more inventory in J open to accommodate such changes, and allocating less C on each flight. This for sure means at the airport upgrading, and being SE you will have first crack at any front cabin seats. However, you might just want to try back a day before the 72-hour Elite window, and again at the 24-hour Prestige window, just incase you've cleared the list. Or at least AC can tell you what the loads are like closer to flight time.