Just because they have that many games that are unreleased doesn't mean that they have that many games that have full internal development teams working on them at any point in time ...
Many software projects (including videogames) tend to have long periods of planning and intital set up which requires a lot of work from a few members of the team and almost no work from most members of a team; and there is often a long period at the end of a project which is centered around testing and debugging (and localization in the case of videogames) which will, once again, require a lot of work from a few members of the team and almost no work from most members of a team. Good management will try to complete the planning stage of a project just as the testing and debugging stage of another project begins in order to keep employee downtime to a minimum.
On top of this, there are a wide variety of reasons why a company would choose to outsource work that they can, and it is possible that High Voltage has choosen to outsource some of its work.
Now, there is lots of evidence that supports that the Wii requires smaller development teams to work for less time to produce a game that is similar in scope to HD console games. All I am saying is that the size of the company and the number of unreleased games don't demonstrate that.