Yes, they were able to show that cloth masks can "potentially" provide significant protection, but using hybrid materials, and also noting that a significant reduction in effectiveness is seen around the edges of the masks. I'm somewhat skeptical that this is practical for mass populations.
The situation with the mask not providing good seal around the edges would be solved with better design. Materials that include an elastic border around the edges should fix that problem. Also, facial hair and beards that would interfere with the seal, should be shaved clean with a razor.
I thought about mask design after my initial reply, and thought about the seal problem of masks around their edges. I spent a lot of hours in my youth under water with a mask. If it had a bad seal, it made the dive miserable. The mask used as an air filter needs a good seal around the edges. Many of the masks I have seen are poorly designed. Try finding one with a flex fit.