Maiden of the mist cant attack inhibs?

so ive only played the new yorick about 3 times so far, but on one occasion my maiden destroyed bot lane inhib tower, but after that it litterally went brain dead. after it destroyed the tower it just started walking back and forth between the enemy blue buff and the base gate of the enemies base. it did this untill someone killed it, and it never touched the inhib. is this intentional? (note, while it was doing this i was in my own base defending mid against a 5 man push)

if it didnt do this and actually destroyed the inhib we would have been in an awesome position to counter attack...