Plain and simple, some things just get missed and overlooked. This is one of the challenges that comes with releasing a new set of cards every year (which no one seems to complain about). Another challenge comes in that the playtest team doesn't always get to test against each other, but rather with a small group within their playgroup. As a result, sometimes cards are interpreted differently (and thus the cards get played differently) by different playtesters without each one realizing it.