This appears to be the case on Linux aswell, beta update this morning refers to the 17th January update, not the one from 30th.
That's how beta updates have always worked. You've always had to hunt down the changelog, although the creation of the 'Steam Beta Client' group makes it a bit easier to do so.
Still I think it should be trivial to add beta notes in that notification.
@Tea23 I know it has always been like that. But the link above proves that Valve has announced that this has (or should have) been changed in the current beta.
We're looking into this, thanks for the report.
@johndrinkwater, how are you seeing the change log? When the update dialog appears or another method?
The beta release notes for the update on February 5th showed up correctly, so I guess this is fixed by now.
Nothing extracted yet.
In the initial announcement for the current beta it is mentioned that the update process will now use the changelog for the beta when opted in.
This does not work, at least on OS X.
PS: Sorry for being off-topic using this Linux-only issue tracker, but as long as there's nothing equivalent for OS X or a general one I don't see any alternative.