The statistic quoted is for "users", so presumably the measurement was made against randomly selected individuals of the general population (though the article frustratingly fails to cite a source). This is important because the effect is not evenly distributed among demographics, per the article:

What’s more, we don’t know why some people are so much more susceptible to it than others, but we know that there are numerous markers that make us more likely to experience it. Women, as mentioned previously, are more likely than men to get VR sick. Asian people are more likely than other ethnicities to experience motion sickness in general. Age is another factor—we’re more likely to experience it between the ages of 12 and 21 than in our adulthood... until we reach our 50s, upon which the likelihood increases again.