Not sure what your point is. The phenomenon you describe is typically the result of an above average snowfall over the course of a winter rather than a lack of forage to sustain the herd. It's just harder and more exhaustive for animals to get to the food. Large foraging animals tend to congregate where movement is easier, such as plowed roadways, but it doesn't assure them more forage. The same thing happens in Alaska during winters when above average snows are too deep for the animals to move and restricts their ability to forage. The moose get killed in above average numbers by trains and cars because they won't readily move off the roads or tracks to fight the snow. We typically see buds stripped off saplings by the moose nearer the roadways, but plenty of food left a few hundred yards off the roadways. It's just too much effort for the animals to get to it.
It doesn't matter whether populations grow unchecked, or if they are limited by hunting and wolves, hard winters will kill many even in healthy, sustainable herd populations.
That's a good point.