Correct, @grimmie. I’ve deleted extra commands / buttons without issue. 
EDIT: I looked through my most recent notes, and seems like for DELETE I didn’t have a data component (the -d “{}” part at the end). It was just:
curl -i -H "BOND-Token: xxxxxxxxxxxxxxxx" http://192.168.nnn.nnn/v2/devices/aaaaaaaa/commands/bbbbbbbb -X DELETE