I'm not understanding the importance of distinguishing glue code from non glue code. It's still work that needs to be done whether it's "first class" or not.

I'm not understanding the importance of distinguishing glue code from non glue code. It's still work that needs to be done whether it's "first class" or not. That difference boils down to who writes it, not the fact that it is present in the code base (as measured by LOC, which the author measures and attributes the cause of high LOC to glue code)