Are you sure you read the whole thing?
What I linked to discussed ALL SIDES of the issue including whether it protects the wearer or the people around the wearer. The study itself was about one thing: does a mask make you less likely to contract COVID when used in conjunction with other measuers.
In the beginning, we were told the truth -- if you social distance (~6ft), wash your hands often, avoid large indoor gatherings and limit unnecessary trips to stores and other public places, you're doing as much as you can for avoiding catching it. Masks were mandated as a proactive measure to appear to be "doing something" to stop the spread.
The article plainly states they are not arguing for or against masks on their own, but whether or not making them mandatory along with the other things is effective. They found they are not.
What this explains is why the rate of infection increased when masks became mandatory most places. When you have a false sense of security due to everyone being masked-up, you get lazy about doing all the other things we know are effective. Hence, the argument can be made that masks were counterproductive in stopping the spread.
Some quotes from the study you linked:
“Objective:
To assess whether recommending surgical mask use outside the home reduces
wearers' risk for SARS-CoV-2 infection in a setting where masks were uncommon and not among recommended public health measures.”
“Limitation:
Inconclusive results, missing data, variable adherence, patient-reported findings on home tests, no blinding, and
no assessment of whether masks could decrease disease transmission from mask wearers to others.”
“
Observational evidence suggests that mask wearing mitigates SARS-CoV-2 transmission, but whether this observed association arises because masks protect uninfected wearers (protective effect) or because transmission is reduced from infected mask wearers (source control) is uncertain.”
“The findings, however, should not be used to conclude that a recommendation for everyone to wear masks in the community would not be effective in reducing SARS-CoV-2 infections, because
the trial did not test the role of masks in source control of SARS-CoV-2 infection.”
“
Reduction in release of virus from infected persons into the environment may be the mechanism for mitigation of transmission in communities where mask use is common or mandated, as noted in observational studies.”
“
Although masks may also have served as source control in SARS-CoV-2–infected participants, the study was not designed to determine the effectiveness of source control.”
And from the authors’ response to a comment: “
We have been very clear that we studied the efficiency of masks protection for the wearer – not the effects of face masks when used by an infected individual (source control).So they literally say several times that their study did not measure the protective factor of masks reducing transmission from infected people wearing masks.