It's more like airborne is determined by particle size, particle size is a continuum, and the cutoff point is not universally agreed on. Airborne usually implies a virus much more contagious than covid-19. Learning about this virus began just months ago, so as knowledge increases understanding of it changes. It may be transmitted in smaller droplets than believed previously, but infection also requires greater exposure, which is another factor that makes it less contagious than a virus like the measles. The issue here is that "airborne" is problematic terminology... and yes, there is a concern that people who don't understand this will react irrationally.