IOW, it's the difference between "these words in this poem rhyme" vs "this poem sounds nice because these words rhyme". Which, incidentally, is an analogy I make in the lightning talk to explain why this part would be glossed over: people assume that appreciation of rhyming/iambic pentameter is universal.
[1] "They taught that Shakespeare used iambic pentameter..." https://news.ycombinator.com/item?id=49378069