I'm not doubting your observations, but I think there may be more to it. I've just gotten back into cars recently, and so far my packs have not been too warm at the end of a run and have not bothered taking a temperature reading.

With helicopters, packs get hot because of the discharge rates, and you really notice it when you run saddle packs and dont parallel charge. The pack being charged cools quicker. They do seem to start heating up again towards the end, and even more so with higher C rates. I rarely go above 3C and my packs seem to stay pretty cool while charging.

Next time you do a high C cycle, just out of curiosity, take some temperature readings throughout the process. It's easier to compare when you have saddle packs, but you should still see a temperature curve that looks sort of like a U. If you were to compare it to an identical pack that was just sitting there (like if you just pulled two hot saddle packs from your car), you may see that the one being charged initially cooled quicker than the one that's not being charged. It may still end up warmer at the end of the charge, but the curve will be a U instead of a slope. Had me really scratching my head when I first noticed this, but then I did some searching and found a bunch of studies that got way into all the details. Kind of nerdy, but give it a look.