I think the mechanisms for heat and cold are different. Whenever Thermodynamics is involved,
things are irreversible.
Understand that the higher/lower power/cap relationship between warm and cold is due to the normal battery chemistry going faster/slower at higher/lower temps. That is the normal function
of the battery. These changes take place on a rather fast timescale (i.e. however long it takes the battery pack to reach a given temperature, a few hours maybe).
Degradation is a totally different animal, that is the chemical process that destroys, if my understanding is correct, the electrodes of the battery. I takes place on a timescale of several years ( or so we hope) AND it is, unlike the normal battery operation, NON-reversible.
So hot temps speed this decay up, low temps slow it down, but ill goes in just one direction.
Put a rotten steak in the freezer and it wont become fresh and tasty again.
It might be however that there is an artificial intervention involved in the process, TickTocks cap vs temperature data indicate an almost linear relationship between temperature and capacity, but opposite to what you would expect from chemistry. So maybe the BMS is doing something...?