That's what I'm concerned about, is if it stays locked in an icy, low traction, parking lot and makes the back end lose grip and slide if I try to turn.
A 'locker' will not be the cause of you losing traction. Inadequate tires for the conditions, excessive throttle for the conditions, or inappropriate speed will almost universally be the cause. What a locker 'might' do is result in 'slipping' to one side ONCE traction has been lost (especially on a side hill).
Or do this "BANG" thing that would break the rear free and cause it to start sliding. Still not sure what that is, Jeep people say it happens when they turn while backing out of parking spots.
I don't what it is about the 'Jeep thing' (if anything at all), but I have a couple of auto lockers in other vehicles (70 model Bronco, 90 Model Bronco) that I have hundreds of thousands of miles on and can count on one hand the number of times I've had the sudden engagement 'bang' thing happen. It's just not a concern.
(I go up to the mountains every year and I've witnessed cars sliding down the parking lot with all wheels locked plenty of times. All it takes is a nudge and it's hard to get traction back)
Empirical evidence that 'traction' was not available regardless the condition of your differential. I have seen, experienced and appreciate that 'momentum' (once initiated) on ice can result in a situation where you have little to no control over the outcome (sliding), but again...except for the possibility of slipping to the side (after traction has already been lost), an auto locker has never been a problem for me.
If you should be concerned with anything...it is the propensity for a locker to want to push you straight ahead. Under certain conditions that can be annoying...but usually overcome once you learn how to drive out of it.
At the same time, looking at the gas bill makes me realize how "little" an airlocker costs.
No question a 'selectable locker' is the best of both worlds.