Unless the delibility of ink was a feature they desired. Hypothesizing that they were trying to prevent a working ranger from falling into the wrong hands wouldn't strike me as absurd. Dropping them in a firepit or stream to remove the ink would be pretty handy if you know your military encampment is about to be over-run and you can't save everything.

Of course that leaves the question of the two extra holes. But it would certainly be a status symbol.