As you’ve mentioned, these are not in Microsoft’s security listing and have no CVE(s) tied to them.
https://portal.msrc.microsoft.com/en-us/security-guidance/releasenotedetail/2020-Sep
Microsoft will always produce a .NET release on Patch Tuesday. If the release is not in the MS security listing, it usually means repackaged updates, meaning they are wrapped with a new container KB but the actual update binaries are the same. And if I’m not mistaken, these are always categorized as Security Updates as well, similar to Servicing Stack Updates, which also are categorized as Security Updates but not tied to a vulnerability(CVE).
This is also why you won’t find the typical “Security-Only” updates that are normally paired with the .NET rollups (for pre-Win10 OSes) listed on Microsoft’s security portal.
With this month’s release, there seems to be some updates in Microsoft’s .NET release that aren’t yet in BigFix. Again, MS documentation hasn’t tied these to any security issues but we do understand the concern as these are categorized as Security Updates.
The team is looking into this and will release any missing updates as soon as they can.