In a moderate side impact, it *seems* that they would provide some side protection, because the slider is about the height of a sedan's bumper and should resist side penetration, at the cost of delivering a sharper impact to the 4Runner.
In a high speed side impact with a full-sized vehicle, the slider could bend upwards in unpleasant and untested ways. This may be a reason why most mods are labeled as being designed for off-road use. This sort of impact is deadly to start with, but the vendor doesn't want to be found as a party at fault.