Yes this is an interesting one.
On one hand, we are keen to avoid reimplementing every feature of course and activity completion in badge criteria - if people want more criteria relating to activities or courses it makes sense for them to be added to completion rather than badges. So in this case fixing MDL-40495 would solve the problem.
On the other hand, as Yuliya says in MDL-40755, you may want to issue badges for slightly different criteria to the "completion" criteria. Her example is a good one, maybe the course grade to complete is 50%, but you want to award a "distinction" badge for a grade of 80% or more.
Personally I'm not sure the best way forward with this, interested to hear what people think!
Simon