I think the yes/no answer to the question of whether apple pulled it or not has now become more complicated.
The delta beta update is still available to developers through the mac app store as well as the direct link on apple's developer forums.
But to complicate the situation, it now seems that the combo beta update is no longer available through the mac app store.
But I still maintain that even this hasn't been "pulled" because the direct link for that is still working.
What is strange though is that the combo file size for this 10.9.4 beta is 480.2MB whereas the combo for 10.9.3 on apple's website is 947.2 MB.
Why would a 10.9.4 combo be about half the size of a 10.9.3 combo? That's very weird. I know apple do weird things from time to time, but that might be too weird even for apple!
I suspect that apple may make a better combo for this beta before the next beta is released.
So the answer to the question of whether the beta was pulled is still no, but as for the combo, this may get a new version soon.