This is related to the recent changes to add a ArPow SourceBuild leg to CI in #32790.
In the official CI builds, the Microsoft.SourceBuild.Intermediate NuGet package that gets created is not getting published. This is necessary for the source-build legs of downstream repos that depend on ASP.NET Core.
I speculate this is a simple issue of not passing the _PublishArgs into the source-build job. In order to implement this, dotnet/source-build#2151 must be fixed first.
cc @JunTaoLuo