I think what the article is trying to present, poorly, is that the “relatively rare as a percentage of use” bit may have been because until relatively recently the sample size was significantly lower and the marijuana itself was far less potent.

For what it’s worth anecdotally I have seen a number of people who utilize marijuana, medical or otherwise, for anxiety. I mention this because I work in mental health and regularly give said people anxiety screenings. For a great deal of them their anxiety scores worsen over time as they utilize marijuana. It’s certainly not a study by any means but I’ve had peers note the same and there are some studies that have occurred and are ongoing to the same effect. It’s not surprising; it’s like treating anxiety with benzodiazepines. It lowers the intensity of the anxiety in the moment but as result also decreases your overall resilience towards anxiety as a result because you are less reliant on more traditional coping skills