I think that’s what they meant, and said. Cas9 “CRISPR associated protein 9” is the protein/enzyme that they modified.
I'm definitely getting into hair-splitting territory, but I think it's important to not conflate modifying a protein with fusing two proteins. It would be easy to come away from the GP and think that scientists have the ability to easily change the enzymatic function of Cas9, when in reality they're effectively just connecting a protein to Cas9 and letting it do its thing.