Experience and a basic level of observation would show that you're reaching to find a justification here. It's clear that the masks are covid-related and not pollution related. Gymnastics are for gymnasts not for research.
Why would you ever assume that!? I also wear a mask when riding near traffic. Masks on bikers without helmets were a common sight in Paris in 2009 when I lived there. The mask has a measureable increase in immediate comfort, while the helmet is something that requires thinking ahead. Of course more people will remember a mask before they remember a helmet.