There are parallels of thought here to template and macro libraries.

One issue is that a spec without a working reference implementation is essentially the same as a pull request that's never been successfully compiled. Generalization is good but you can't get away from actually doing the thing at the end of the day.

I've run into this issue with C++ templates before. Throw a type at a template that it hasn't previously been tested with and it can fall apart in new and exciting ways.