I don't know about SMV, but lots of SDO, SBP, SVR, PGA, (and possibly other resorts) owners bought from the original developer, but never joined the network, despite multiple invitations to do so once Starwood took over. These people had "full member" rights if they joined, so I think it's a separate issue from the "can you combine SOs" question (they would have been permitted to combine, even under the old rules).
As an aside, I was told by member services last month that I could combine my various SOs (some from mandatory resale, some from a developer purchase and some are requal SOs). I didn't post about it at the time because I didn't try to do so -- figured I'd wait to see if it works or not. Has anyone actually done it yet?
Edited to Add -- Ooops -- cross posted with Glorian. Sorry about that!