Jack Simth said:some interesting questions pop up:
What's the Wis/Cha of a fireball? If it doesn't have one, then what's it's hardness? After all, if it doesn't have a wisdom or a charisma score, it's an object. If it's an object, it has a hardness. Likewise for Bear's Strength, Owl's Wisdom, and the like.... also for the air ... hmm...
Of course, if you make a third category that spell effects can potentially fill (neither object nor creature), then you can deal with such oddities.... but that would be a house rule, technically.
Is it a house rule?
Are spell effects defined in the game? Yes.
Are they listed as objects? Not usually.
Are they listed as creatures? Not usually.
There are a lot of effects in the game that are not creatures and are not objects. They have no Wisdom. They have no hardness or hit points.
That one sentence is in error with respect to everything in the game. It is referring to the subset of creatures/objects (i.e. physical things in the game) and not magical effects.