@Override
	public DataType toDataType() {
		Structure rowDt = new StructureDataType(new CategoryPath(PATH), "AssemblyRefOS Row", 0);
		rowDt.add(DWORD, "OSPlatformID", null);
		rowDt.add(DWORD, "OSMajorVersion", null);
		rowDt.add(DWORD, "OSMinorVersion", null);
		rowDt.add(metadataStream.getTableIndexDataType(CliTypeTable.AssemblyRef), "AssemblyRef", "index into AssemblyRef table");
		return new ArrayDataType(rowDt, this.numRows, rowDt.getLength());
	}
Describes the AssemblyRefOS table. Apparently it is ignored by the CLI and shouldn't be found in an assembly.
Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/pe/cli/tables/CliTableAssemblyRefOS.java