Visual COBOL Build Tools for Windows is a component of Visual COBOL which offers the same compilation, build, and execution functionality as Visual COBOL. However, as Windows containers do not support graphical user interfaces, using Visual COBOL Build Tools for Windows gives you all the required functionality of Visual COBOL but without the disk space overhead of an IDE.
The Docker demonstration to build the base image for Visual COBOL uses Visual COBOL Build Tools for Windows.