I would think that AEB would be applying the brakes hard to avoid an imminent collision. That is, your 10-20% regen speed drops were probably not AEB.
My guess is that TACC is primarily concerned with following, but Autosteer (beta) forces the system to take more information (or misinformation) into account.
It is great the FSD enhancements can trickle down to non-FSD functions like TACC, but the problem is that the FSD failures trickle down, too.
For my part, I am on 2022.4.5.3 and after disabling Autosteer (beta), my TACC has been performing pretty well. Only a couple of minor slowdowns. (I have been driving mostly 2-lane roads and suburban arteries.)