I am not a lawyer, but that argument just doesn't sound logical. PAR says it is not imposing any restrictions because PAR uses the Artistic License. It also says that you should feel free to include other modules that use the Artistic License because those modules won't have any restrictions either. But it never
says that you can only
include modules that use the Artistic License! You might have problems with GPL modules, for example, but if Bob gives you a module under "Bob's license" that allows you to include it in a PAR package, common sense tells me that you free to do so.
So I think the problem is between you and the provider of the module that you want to include.