By default Impulse is downloading Alpha/Beta versions of updates. I'm not sure whether this is the default state for Impulse, or a carry over from my SDC account, but either way it should not be the default setting. In the case of SDC carry over it should be remembered that for a very long time SDC had "Download Alpha/Beta releases" on by default, a checkbox which I'm sure has been the cause of one than one support ticket to Stardock.
More sensible surely to disable this, and thus people who get alphas and betas have specifically opted-in.