Maybe it's a translation issue, but this article doesn't really answer the question at its root level and keeps referencing recent events - obviously Russian troops in Donbass are concealing their identity, but Eastern European troops have been wearing ski masks for decades now. Why? I'm not sure "to confuse the senses" makes sense, since for 100+ years warfare has happened at long distances.
My money is on the fact it's cold and windy often.