ArchLoader.LoadModule() sets the name of referenced assemblies only for the requested assembly, not for other loaded assemblies.
I think you can retrieve this data from an AssemblyDefinition via the MainModule.AssemblyReferences property, so instead of calling
_archBuilder.AddAssembly(assemblyDefinition, false, null) you could set the referenced assembly names inside of the AddAssembly() method.
I'd like to open a PR for this issue.