Thebian and JustJohn…again, two users of the White Wolf forums, have kindly educated me about an aspect of the Mage rules that I had never really used properly – the distinction between fixed and free Quintessence.
Prime 3 is enough to channel free Quintessence, but fixed Quintessence (which things are made of) requires Prime 4 (for inorganic) or Prime 5 (for organic) to turn into free Quintessence that the caster can use.
Thus the “thirsty blades” of the Mage Storyteller’s Handbook were doing Prime 5 effects. In the 1st edition rules, they would have been five-dot Wonders.
When I look back at how 1st edition was written, there is a Prime 4 effect for destroying inanimate objects only. The authors could have gone the extra mile and explicitly articulated the notion that Prime 5 would allow a similar effect on living things.
Page 215 of 2nd Edition – A rank 5 variant destroys living beings.