That doesn't seem to be the game that Google is playing. How many users actually know what version of Chrome they're running? It auto-updates in the background pretty much silently. Google probably wants to make it as much like gmail as possible -- do you know what version of gmail you're running?
It's also the same model the Linux kernel uses. Given that the 3rd number is the only significant one these days, we might as well call the latest linux kernel "38.rc8".
So no, I don't think it's marketing -- I think it's just good engineering. Using the Linux kernel as your model for release cycles is probably not a bad idea for most projects.