Yes, I read the finding, but the authors weren’t confident enough in their results to say that masks would or can prevent transmission. Instead they said could.
That’s the first thing I check in an abstract. Without a definite finding a study provides little more than interesting reading, conjecture, and possibly a point for further study.
I don’t think anyone disputes that barriers can inhibit droplets. How about virus not in droplets or aerosols?
The cdc stated about a month ago that asymptomatic patients do not shed virus so the pertinent studies you mention are dated.
Here is what WHO (for what it’s worth) said on June 9th about the spread of the virus by asymptomatic carriers:
https://www.statnews.com/2020/06/09/who-comments-asymptomatic-spread-covid-19/
Here is a preview (pre-print) on the CDC website of an article to be published in July of studies of the spread of the virus by asymptomatic carriers:
https://wwwnc.cdc.gov/eid/article/26/7/20-1595_article
Our knowledge of many aspects of the coronavirus (origin, spread, treatment, and mortality) is seriously incomplete and ever-changing.