I agree. Verification of things that are internal is at a seller's word. Engine guts are one. Is the water pump a high volume pump? A shift kit in a trans is another. What's the ratio of an Atlas transfer case if it is installed in the vehicle?
Yes, buyer beware. But if a person "swears" that it has a component that it didn't, using specific buzzwords like "chromoly shafts", he is still a liar. Should muddypaws have verified it? That's debateable. Should the seller have lied? No.