The Manifest mechanism only applies to the modules packaged inside ear and not standalone modules, but it's not really relevant here as the jar as attached could deploy to v2 successfully. :-)
Looking at the v2 code, it seems it added all the root level jars of the modules to the classpath regardless of whether the libraries are referenced or not. This is why the application could deploy to v2 successfully. This is not a spec defined behavior which is not supported in v3 now. We can probably expand the functionality of "compatibility" property to include module level jars as part of the jar visibility backward compatibility support in v3.1.
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