This is an issue i bumped in a while ago, don't know if it is by design or a bug.
Would strongly support this as a new feature request. Creating NPM Groups and not be able to filter on it, makes not much sense.
RJager, we were able to get this submitted into SolarWinds as a feature request. If need be, feel free to reference our ticket number 304119 for updates?
We would really like to see this changed. It's being debated as to whether this is a bug or a feature change but I can see the argument both ways. It just seems to a user who's using this for the first time, this would not be a very intuitive approach to using this filter.