Im sure it’s required. I got a geology buddy and he said this is pretty normal for identification of rocks. So I bet its a required skill to tell spicy rocks from rocky rocks.
Geology degree here - you identify some rocks by licking them. Licking most rocks will give you no information. But in a final, honestly, nobody would bat an eye if you licked all of them, just in case.
I have to know, how was sanitation handled? did you each student have an individual sample, or were you all licking a communal rock?
Was a thing when I took geo in first year, rock test (and the professor) was kinda a legend within engineering.