I read that link on idioms, but I think the author misunderstands the nature of idiomatic expressions.

Idioms are simply non-literal expressions. They are figures of speech, such as “this is a stick up”, “he got paid under the table”, “I got smashed at the party”, and “he’s under the weather and isn’t coming to the party.” Their meaning cannot be deduced from the literal definitions of the component words but refers instead to a figurative meaning known through conventional use.

We have them in Japanese too. Someone who is very sensitive to hot drinks (tea/coffee) or hot soup has neko jita (cat’s tongue). A sheltered daughter is hako iri musume (literally a daughter kept in a box), buta ni shinju means “pearls to a pig” and refers to someone who doesn’t appreciate the value of a high-end gift they received.

Sometimes proverbs include idiomatic expressions, but I see no basis for his statement: “Idioms and proverbs—especially idioms—are crutches: recycled phrases that have outlived their value, only we’re too lazy to replace them.”

well, that's ice in the ol' urinal.