I agree with the reply, but it's still odd. The list is matter disruption, and I can't see why the spell should be limited to inorganic matter just because no one wants it to be used on *living* matter. It is an evil Essence list, I have trouble finding a reason why stone and metal would be OK but wood would not. It would be OK if there was a "organic matter disruption" spell somewhere else, but there isn't.
I am squarely under the impression that the authors wanted to avoid the use of such spells on living matter (because it would essentially be a 'RR or die' kind of spell, and we all know that such spells are only found in the Black Channels list :-p). But excluding wood (what about petrified wood ?), cotton and all kinds of cloth, alcohol and basically all kinds of carbon compounds (coal, sugar, oil...), just because the spell is poorly worded seems being overly pedantic to me - having the spell work on water (inorganic) but not on oil, on air (mostly inorganic) but not on methane, ammonia, carbon dioxide and others, or on ruby but not on diamond, makes absolutely no sense to me.
I would house rule it into "inanimate" matter. Or "unliving" if you want to be even less restrictive (the difference being "inanimate" doesn't work on a stone golem or an undead, but "unliving" does).
Still, it's a F spell, not a U spell. Matter gets a RR. Wood, if affected, might have a lower level than iron