thighhighs and stockings

Was this implication put backward? Seems to me thighhighs are stockings, but maybe not all stockings are thighhighs. But if all are, it should be an alias instead?

Predicate Consequent
stockings thighhighs

This was done for convenience purposes. Stockings are thighhigh socks usually made of sheer fabric and lace, and usually worn in conjunction with garter belts. They're less common than regular thighhighs, so this implication was created as a compromise.