More explicit, but not greatly different from what the US constitution and the common law indicated.
When the states ratified the Constitution, i'm pretty sure the slave states thought they were getting the things you mentioned in your message. Since they felt as if they were given a bait and switch, I think they wanted it spelled out clearly so that no one in the future would mistake the meaning.
“More explicit, but not greatly different from what the US constitution and the common law indicated”
Greatly different in one way. Under the Confederate Constitution, slavery was mandated in all Confederate states and territories. In the United States Constitution, slavery is not mandated. A state could outlaw the practice if they so choose. By 1860 15 states had made the practice of chattel slavery illegal, and it was illegal in all Territories of the United States.