I showed the pictures to another group of older Mongolians - they said the sticks were Chinese and the people throwing them were Chinese too even though there's a wall scroll of Genghis Khan in the background of one of the pictures.
Many Outer Mongolians don't consider Inner Mongolians to be "real" Mongolian because they're culturally Chinese, maybe that's what they meant. It's also very well possible any memory of the sport was lost during Soviet times.