Yes, it's as Zini said. Open a workspace containing (say) 6 projects. Change a few of them then save each project. Next time you open C::B they'll appear at the top of the Recent projects list. In fact, if there are a lot of projects, you can end up losing your workspace off the bottom of the list, which is really quite annoying.
I'm running version svn5859 but this has been standard behaviour for as far back as I can remember. It's one of those things that I've always meant to suggest but never quite got around to it.
I like the idea of not adding projects that are part of a workspace that was just opened.