The ENTRY stmt was designed primarily for specifying alternate entry pts to subpgms. The primary entry pt is supplied automatically by the compiler.
I've never tried to execute a pgm from the JCL EXEC stmt using an alternate EP. It should be easy enough to test. But remember, that subpgms usually process data passed from the CALLer. This you can't simulate from the JCL. (You can, really, but it's messy.)