Yes they do. I have bought many mods on Steam that were early access, most recently the Harrier.
I understand that 2.5 is an alpha and don't expect it to be bug free. The problem I see is that if your an MP guy most of the MP servers move to the OB/OA right away. This forces all of us MP guys to follow suit. So even though its an OB/OA it might as well be a stable release. Thats what makes this bug game breaking alpha or not.
Maybe this is a community problem and not an ED problem, I don't know. Either way if your a Steam user you get the short end of the stick this time.