Well actually when you dig into the data sheet it states that it'll discharge at upto -20C but charging isn't happening until 0C - which makes sense and is expected for lithium batteries.
Again, if your current battery is functioning fine - what's the point of swapping it out for this battery?
The current 12V battery is also maintenance free, so that's not an advantage now is it?
Neither is the higher energy density when your HV battery is doing the work and the 12V only does 2 seconds of work at the start.
However, if you got money to spend and just want to tinker, go for it.
But if you're wanting piece of mind, then I'd spend the money on the battery booster I mentioned before.
I was looking at this route when I first got my Soul because I'm interested in camping and love to tinker. Without a doubt if someone wants to run 12V accessories and/or add solar in the mix - using such a battery makes perfect sense. Higher energy density, lower weight, better charging efficiency - what's not to like? Well if you just leave the car on, none of that matters.
In the future if I do go this route, I'd probably keep the old 12V battery and swap it back in as the temperature drops. However for now, I don't think many Soul EV owners will benefit much, if any, by "upgrading" to a 12V lithium battery, unless they plan on doing some other things with their car, or if these become cheaper than the traditional battery.
As for the vehicle charging it correctly, looking at the data sheet it states that it has a BMS and will automatically cut off charging when it's outside of parameters, so you should be perfectly fine in that regard. Hope that helps.