Just documenting what I've found here
1. I scoured the site to make sure I didn't have an orphan learning plan with the competency it in. Nothing
2. Made sure the learning plan link (from profile page) was empty
3. Checked the data base and in the mdl_competency_usercomp table there is a record for a competency being linked to my id (admin).
I don't know why this remains in the database but it is clearly why I'm not allowed to delete the framework. Apparently it didn't get deleted from the table when I deleted all the learning plans.
Continuing with the test, I deleted that row from mdl_competency_usercomp and BAM! Now I can delete the framework.
So, here is my guess. When the learning plan still existed, I associated the framework in question with it and awarded one of the competencies within it to myself. When I later deleted the framework the assignment to me was not. Maybe this is because I did all of this as admin? Maybe (hopefully) this is not an issue in a 'normal' situation (i.e. a teacher etc. assigning a competency to a student)?
At any rate, I'm back to the beginning where I can start with a clean slate.