Visual Studio Build Tools 2019 Offline Network Layout - Packages Missing from Layout Cache

Question

I'm attempting to create a network layout of a selection of the latest Visual Studio 2019 Build Tools components (v16.11.12) using the following command:

vs_BuildTools.exe --layout .\ --add Microsoft.VisualStudio.Workload.AzureBuildTools --add Microsoft.VisualStudio.Workload.DataBuildTools --add Microsoft.VisualStudio.Workload.ManagedDesktopBuildTools --add Microsoft.VisualStudio.Workload.MSBuildTools --add Microsoft.VisualStudio.Workload.NetCoreBuildTools --add Microsoft.VisualStudio.Workload.NodeBuildTools --add Microsoft.VisualStudio.Workload.VisualStudioExtensionBuildTools --add Microsoft.VisualStudio.Workload.WebBuildTools --includeRecommended --lang en-US

This downloads the relevant packages as expected so next want to test the installation using the Response.json file with the following command:

vs_setup.exe --wait --noUpdateInstaller --noWeb --in CustomInstall.json

CustomInstall.json contents:

{
  "installChannelUri": ".\\ChannelManifest.json",
  "channelUri": "https://aka.ms/vs/16/release/channel",
  "installCatalogUri": ".\\Catalog.json",
  "channelId": "VisualStudio.16.Release",
  "productId": "Microsoft.VisualStudio.Product.BuildTools",

  "includeRecommended": true,
  "quiet": true,
  "norestart": true,
  
  "addProductLang": [
    "en-US"
    ],

    "add": [
        "Microsoft.VisualStudio.Workload.AzureBuildTools",
        "Microsoft.VisualStudio.Workload.DataBuildTools",
        "Microsoft.VisualStudio.Workload.ManagedDesktopBuildTools",
        "Microsoft.VisualStudio.Workload.MSBuildTools",
        "Microsoft.VisualStudio.Workload.NetCoreBuildTools",
        "Microsoft.VisualStudio.Workload.NodeBuildTools",
        "Microsoft.VisualStudio.Workload.VisualStudioExtensionBuildTools",
        "Microsoft.VisualStudio.Workload.WebBuildTools",
    ]
}

The problem is that the pre-check verification fails with the message

"Pre-check verification: The following required packages are missing from the layout cache"

This message is followed by a large swathe of packages that are indeed missing, but if these are required, I'd expect the initial layout command to include these! The suggestion is to run the fix command:

vs_setup.exe --layout  C:\Temp\2019BuildTools_16_11_11 --fix

However, this just completes saying everything's fine.

Even running the layout command again in another directory, but this time downloading all packages doesn't provide what it says is missing so am a bit stumped as to why the installer is looking for packages that aren't included as part of the full install e.g. error log says 'Microsoft.Net.Core.BootstrapperPackages,version=5.0.0.45' is missing but only 'Microsoft.Net.Core.BootstrapperPackages,version=5.0.0.47' is available in the cache.

I initially created this post in the wrong forum but thought I'd solved it due to having the "installOptional" parameter present in my CustomInstall.json file but not in the layout command, however, looks like it's still not working after removing it.

Am I missing something?