I frequently get pinged on when a new Cumulative Update gets published on Microsoft Update Catalog, and why it is not in OSBuilder. I hope this will clear a few things up.
I posted previously on this last week, and maybe Microsoft reads my stuff and decided to clarify things ;)
Michael Fortin (Microsoft Corporate Vice President, Windows) explains in some detail about the different updates
And here is the important stuff ...
These updates will consist of the "Patch Tuesday" (B Release) and the on-demand updates. C and D releases are considered "Preview Releases". This explains why you don't see them in WSUS
The Microsoft Update Catalog will contain ALL releases. Patch Tuesday Releases will be classified as Security Updates
Another method to determine the Latest Cumulative Updates is to view the Windows 10 Update History page.
This will detail the updates that appear in the Microsoft Update Catalog (ALL Releases)
OSBuilder Update Catalogs are generated from WSUS, so these will include the "Patch Tuesday" (B Release) and any On Demand Releases (Critical). C and D Releases can be added to OSBuilder using
New-OSBUpdate, but at least consider that these are Preview Releases and probably should only be used for Testing, and NOT for an Enterprise Deployment, but that's your call.