Natural Law was there before Christianity. Jews, Muslims, and non believers have also understood, and upheld it. The fact that Catholics use logic doesn’t mean logic is a Catholic invention; the same with the Natural Law. Protestants upheld and affirmed the Natural Law in the USA, for instance, long before there was much Catholic influence here. Jefferson, no friend of Catholicism, took it for granted.
Protestant denominations never developed a different view of the Natural Law. Perhaps
some ignore parts of it now, that is not the same as defining it differently. It is likely atheists ignore parts of it nowadays too. That doesn’t mean there is a different “atheist Natural Law”. The Natural Law was widely understood and accepted, the sharpest break against it on a large scale was Germany, in the 1930s and 40s. The enemies of the Natural Law survived World War II. Their continuing success in attacking it does not mean it is less valid. The Nazis didn’t develop an alternate view of the Natural Law. They ignored it.
St. Thomas clarified some aspects of the Natural Law, which was already present before him. He was a brilliant scholar, not infallible, and some of his insights, as well as others, are incorporated into the Catechism. The Catechism does affirm the Natural Law, just as it affirms Art, Logic, and other things. That doesn’t mean the Natural Law, or Art, are Catholic limited things. The Catechism is the authoritative standard you should evaluate Catholic doctrine.