This is an article from a historian, i.e. not an expert on medicine. What is argued is that we haven't disproved that mask works.
The problem is that this doesn't mean anything. For example, we haven't disproved UFOs. We haven't disproved aliens are watching us. We haven't disproved ivermectin.
Now, we meet people who insist that UFOs exist, aliens watch us, or ivermectin is the cure for covid, and we are skeptical about them.
If you read the article, the author only writes that masks aren't disproved of their efficiency and that it was wrong to say masks don't work.
So, a good scientist would understand that there's only weak evidence for the efficiency of masks raised in this article. The author probably knows that. In that sense, he hasn't lied.
However, I suspect he also knew that ordinaries would read this article and jump to the conclusion that masks do work.
We don't prove negatives in science, or in medicine. We just know that in the studies we have performed, we have not noticed any meaningful effects and we can conclude there is likely no observable benefit to taking the drug for that purpose.
The worst part about it is that we HAVE disproved mask mandates. After years of them enacted across entire populations, like state wide mandates, we have more than enough examples to show that long term the effect on spread was absolute zero.
Just look at the CDC study this very article links to in order to see how bad the "proof" is on a population level. They cherry pick a specific period of time in a specific place, and compare places with mask mandates to those without. With the timing lined up just right where the places with mandates had just gotten out of a HUGE surge, while the places without were just getting hit with the traveling wave. Pathetic