I thought that's what happened originally...now that they're back up, isn't that a sign they're ready for download?
"The Spring Update for Windows 8.1 has been added back to Microsoft's Windows Update servers, and we have the links for x86, x64 and ARM versions below. These are official, and there's no reason to assume they are not RTM...."
They then go on to say,
"You can of course opt to wait it out and let Windows Update work its magic sometime at the beginning of April when it'll be rolled out worldwide. Or take the plunge and install now, please do note that the updates require multiple reboots, and may also be pulled from the download locations at any time, like what happened last time.
If this is the first time you're hearing about the Spring Update (or Update 1) you should probably wait for the official Windows Update roll-out, see what's new here for more details on what the update brings to Windows 8.1."
Which makes it about as clear as mud...a disclaimer of sorts, I suppose.
This is why I referred back to the Neowin article in the OP as well as it being the source.