I have never doubted that Alpha 4.x is the Beta. What I can't get my head around is this:
If the plan always has been for Alpha 4 to be released mid-May two weeks before Premium Beta then why not just say that? Why beat around the bush?
What "last communication"?
I'm guessing Michael is referring to the "two weeks before Beta-statement" you quoted above since DB has, at least as far I know, said nothing else about any build before Premium Beta. But in this statement he referred to that as an early build of Premium Beta, not Alpha 4. While still technically "accurate", this isn't really crystal clear, is it?
If this is the plan, then just say: "We are aiming to release Alpha 4 two weeks before Premium Beta. This build will then after bug fixes be the basis for Premium Beta build 1."
There done! I don't think anyone would have any (huge) objections against this AND it would make sense.