Is this only for people using the "linked numbers" feature? Edit: I guess that's actually the normal way of using GV! For weird personal reasons I'm using GV without a linked number, and I still receive SMSes at GV.
That's not weird at all. I've always used Google Voice on its own, without forwarding calls/messages to a "real" number. By abstracting my phone onto a web app, I had the benefits of Handoff years before Apple introduced it.