We are using groups in our Moodle in all courses, and we need exactly that - email to be sent to Facilitator for that group.
Unfortunately Custom certificate is not working that way, and we need to create separate activity "Custom certificate" for every group that we have in every course, and most of the times we are creating 20 - 30 certificates in one course restricted by group.
Another bad thing is that our Facilitators doesn't have ability 'moodle/course:update' and that makes them invisible for the plugin, that ability belongs to Instructional Designer team. Much better solution in that case will be person who has ability to grade assignments, because in every case people who are Teachers or Facilitators have ability to give a grade, and that will make them visible within the group as person who should be receiving emails.
I hope that will be implemented soon.
Just to add at the end, this plugin is great and we are using it in all our courses.