Driving downhill in a front wheel drive vehicle while off the gas can put engine braking force on the front wheels. Would putting it in neutral help if you started to lose control? Out here on the left coast we are usually close to zero when it snows and this seems more slippery than snow in colder temperatures.
I'm not sure because the intervention of the transmission complicates things. Obviously there is engine braking when you pull off the throttle suddenly, and this will cause engine braking on the front wheels, which will tend to make the back end "loose". If it's really slippery, there is even a risk of the front wheels breaking traction.
Beyond that it should depend on the engine rpms relative to what gear it's in.
This worries me coming down steep slippery hills with the Escape Hybrid. Presumably the slip&grip awd system isn't smart enough to spread the engine/regenerative braking to all four wheels. Compared to the Grand Vitara with permanent awd AND a low range the Escape is nerve-wracking to get down such hills. It's something we do all the time, going through the zero degree transition on snow/ice as we travel the winter coastal mountain logging roads.
If it's a really slippery steep hill, the best thing to do is put the vehicle in neutral, partially apply the parking brake, and apply/release the main brakes as needed. Be ready to disengage the parking brake at any time. The reason here for putting it in neutral is that at very low speeds, the engine is pushing the drive wheels to turn against the brakes, making the non-driven braked wheels more likely to lock up and slide first. The main brakes are heavily biased toward the front wheels, and applying them on very slippery surfaces commonly causes the fronts to lock first, which means loss of steering. Using some parking brake balances those forces while not contributing to locking the front wheels. Of course all this was before abs, so it may be different now.
I've seen a line of cars creeping down the snow-covered Cypress Bowl road, every one of them slewing the front end sideways because their front wheels were locking up from braking, with someone on foot running up the line telling every driver to put their transmission in neutral.
And if you should happen to have a Subaru Loyale/GL, beware that for reasons known only to Martians the parking brake is on the front wheels.