I posed that same question somewhere else but silence was the only answer I got.. Maybe you will have better luck?
I can only add my inofficial view on this subject; of course the game is a very important design tool as well - and it makes perfect sense that course designers should have access to it to test-drive and fine-tune their creations. The gents at PP strike me as being a sensible lot and I'm absolutely certain that they do understand this basic correlation of the chicken-and-egg variety.
Having said that, the purpose of the current CF private beta is NOT to churn out new courses - and also NOT for course designers to happily go about doing their thing from A to Z - but to thouroughly investigate and test the current iteration of CourseForge in all its intricacies, to find out which parts are useful and which ones could do with improvements. We do not need a working game for that yet. It would be nice to have it, but it's not essential at the moment.
With CF being in private beta and hopefully soon in public beta - and the game still in it's alpha build, I would estimate that we need to wait for the game to progress into beta as well for it to become a viable option for designers to use.
Waiting is hard and we all wish progress were quicker, but let's not get ahead of ourselves. Testing course designs with the game will happen, simply because it makes no sense at all that it shouldn't. It's just that we are not quite there yet. Rome wasn't built in a… aw, you know...