Unless there’s combat going on in antartica, or the actual artic (wait a few years maybe), generally there is still gonna be a lot of black and dark green shrubs and trees sticking up and around. This guy is german, where even in the depths of winter there is still brush and forest. Laying out in the middle of an open white field, with no cover is stupid no matter how good your camo. Yet if he wore pure white, he would stick out from the available cover just as much. These are professionals, who know what they are doing. He’s balanced to the varied environment. Plus: From a couple km’s away, he might look like a tiny momentary flash and then your dead.