You might want to use better reference than Phil Kaplan. He's not exactly a respected authority on the topic. It's kind of like quoting Ronald McDonald on the health properties of fast food.
Excess amino acids can be metabolized (oxidized) by the liver for use as fuel or to be stored as fat, but his quote is definitely misleading. The spike in serum amino acid levels actually appears to be what gives whey its anabolic effects.
I recommend you read,"Slow and fast dietary proteins differently modulate postprandial protein accretion," by Yves Boirie, Martial Dangin, Pierre Gachon, Marie-Paule Vasson, Jean-Louis Maubois, and Bernard Beaufr?re for a better understanding of this topic.