So you raise an excellent point. In a perfect world, people would use the little doe-foot applicators that you can find on the end-caps and the beauty studio counter, dip in once, swatch, and then grab a new applicator. The reality is that's not going to happen, and unfortunately there are items that are just really sketchy to use at Sephora. It was impossible to keep everything clean when I worked there, but I would usually hide a mascara tester in one of the drawers and that would be my go-to when I was working on clients because out of all the makeup, the mascara is the one thing you REALLY don't want to worry about cross contamination with.

If it were the everyday consumer swatching out of the tube I wouldn't be surprised, it was just the fact that a seasoned MUA with actual credentials wouldn't think about the hygiene aspect when that's usually so hammered into a professional's head.