Certain Hot Fixes are missing from Protect.
Certain Hotfixes from Microsoft are only offered by request.
One of the criteria for a patch to be added to the Protect data is it must have a publicly available download URL.
Example of Microsoft Hotfix Request Form
These patches/hotfixes do not offer a publicly available download URL, and therefore are unable to be added to Protect.
Here are some known hotfixes that this article applies to:
Protect Version: 9.1+
Patch for Windows Servers 9.3+