I think lower temps give higher estimated battery capacity for some strange reason.
.
I tried making a correlation with temp vs. CAC rise or fall. What I've found, even now with my pack, is that its really dependant on each individual brick it seems. I've seen the opposite of what you saw, that when temps drop so does the CAC such as winter. And when temps rise the CAC climbs with it such as with summer temps.
I feel there's so many variables that it'll be difficult to map what's going on as a trend unless we have a good way of tracking it taking into account as many variables as we can capture. Would love to get that going, I think it'd be good. But it'd take dedication and devotion to update so I don't think we'll really get an end result.
I've seen CAC just dive for no reason, I've also seen it recover. All while treating the pack in a good way. Sometimes you may need to take the Roadster out for a long Range mode drive. It could be a good thing for it. But without the data we just don't know what's really going on.
Truly it comes down to your weakest brick, and that brick alone governs the health of the entire pack.