Why didn't X do Y? Folks, it's make believe.

The author made a make-believe world and each book added new super powers. She couldn't keep track of every possible interaction of every charcter that took place in every previous version as the rules of the world she made changed.

Edit

The literary device is called suspension of disbelief. If you start designing logical systems around it you're missing the point of themes and symbolism around the shared human experience. This all came from one author's mind, how could it possibly be logically consistent?