In common usage (I've never heard it any other way in 24 years of software dev) "included in the same executable" means either combining the source files, or linking object files, or similar. "Bundling" means shipping together, packaging together and never, ever has meant "in the same executable". You do know that .zips .gz and other packages aren't "executable" in the sense used by the GPL, right?
The example of an installer can't be more unambiguous. I quote "No. The installer and the files it installs are separate works. As a result, the terms of the GPL do not apply to the installation software." No. Full-stop. GPL does not apply.
If an installer of GPL software doesn't have to be GPL then certainly unrelated software which happens to come in same disk/download doesn't have to be.
Yeah, njharman describes bundling as I understand it as a programmer. What did you mean by "bundling"? If it was "Packaging two programs in the same archive." or "Using Cygwin Bash to kick off our proprietary program.", then those activities are unambiguously permitted.
"If the modules are included in the same executable file, they are definitely combined in one program."
Piping programs into each other is okay, but once you start bundling it's all up in the air.