It can be evidence without being conclusive evidence. The virus may have a moderately high R0 but a large majority of the spread is driven by a small minority

It can be evidence without being conclusive evidence. The virus may have a moderately high R0 but a large majority of the spread is driven by a small minority of spreaders. Most people who have it don't end up infecting anybody else even if they don't take sensible precautions. Now, dressing the hair of 100 people is a lot worse than a normal person's not taking precautions but it might be that they just weren't shedding enough virus to infect anyone in the length of a normal appointment while only talking at a normal volume. Again, this isn't convulsive evidence but it is evidence and generally all the evidence looks to be stacking up on the pro-mask side.