Correct. Studio Artist does not include the "Project" capabilities. This does not mean you cannot master a song, it just means you won't be able to burn a CD or have access to some of the tools mastering engineers use to analyze their work.
I don't see why you can't use the Mastering Suite that you have in Studio One v2. It just won't be integrated.
In other words, simply import your mixes (that you create with Artist).