Exactly. Those aren’t “masks”, they’re balaclavas. I have several myself. I considered them essential, when working (and playing) outdoors in cold northern Canadian winters. If the Russian soldiers were wearing them for concealment — then, judging from the photos, a lot of them didn’t get the memo.
BTW, balaclavas are named after Balaclava, a town in Crimea.
It doesn’t look that cold.