This is true, and even if it did, having a second school is not an uncommon thing. Death can use storm magic for harder hitting spells (as seen in game). Don't believe me? Watch what happens when you load a hex, curse, and feint with a tempest.
No storm puns here, but sparks fly.
I do recall one of Wizard Cities problems involved a certain faction of undead who used storm magic. Maybe part of the storyline? Possible spoiler?
Same principal as the book "Chicken soup for (whatever)". Isnt about chicken soup, took me a month of therapy to get around that one.