Why doesn't gulp rigger accept different extensions is there an alternative?

Question

JavaScript

There is such a plugin for gulp rigger , it is needed in order to inline one file into another. But he has an incomprehensible feature; he does not allow this to be done if the files have a different extension. Moreover, he does not write this anywhere and simply stops working for no reason. Explain this logic to me if it's not difficult. And are there any alternatives to this at the same level, that is, also a galpa plugin?