This is more about AY revenue management but came about as I am watching revenue space waiting for upgrades to clear.
I am using expertflyer and watching daily, noting down availability of all classes relevant indexed against days/hours left to take-off. Currently I am in the period before tings are supposed to happen with the waitlist, but it is striking how little change there is in revenue avilability.

On a supposedly well selling, hard to get upgrades route on likely popular dates the expensive buckets (J, C) are mostly wide open, mid bucket (D) has few seats and everything else at zero.
Sometimes a cheaper bucket "flickers", goes from zero to one for a short time and then goes back to zero. More expensive buckets do not change during that time, and specifically since the expensive buckets do not go down when the cheap bucket disappears again I read that as they tested the market by opening a cheaper seat for a short while but there was no sale.

Interestingly, sometimes J and W moves identically, just as C and E seems to be linked. I take this to mean that they kind of treat Business and PE availability and pricing co-jointly. Possibly with the logic that "we offer 9 seats in C and in W without having 9 seats left in both cabins, since if we sell a lot of W we have waitlisters that can move up and make that room".
Further, when the last seat in C is sold, both J and W goes down to 8. A few days later they open up 1 seat in C again, and 1 seat in E is simultaneously opened.

When this pattern is not observed (ie E changes independently from C), I take it as there is not a large waitlist between PE and J and/or PE has more seats available than Business.

Anyway, long story short, my reaction in this T-70 to T-30 period is that there is surprisingly little activity by revenue management and by customers. I think others have also noted that there keeps on being C/9 all the way down to T-30 and then suddenly stuff happens. And this makes me wonder why they wait so long before waitlist process starts. If no seats are sold between T-60 and T-50 eg, keeping 9 seats open for 20 more days seems overcautios.