As the other commenters said, it's about testing your palate vs. your tongue. I made a mistake in my original comment where I said you don't have a sense of tas

As the other commenters said, it's about testing your palate vs. your tongue. I made a mistake in my original comment where I said you don't have a sense of taste without smell, I meant to say you have only taste (sweet, sour, salty, bitter, umami) absent the flavors your olfactory equipment provides.