I recently completed a three part Google Assignment project with my students. My students had to submit shareable links to several different documents on one hyperdoc. The use of shareable links was new to them and many submitted projects contained incorrect links. I would comment on their hyperdoc and unsubmit the project so that they could make corrections. Students were completely unaware that I had done any of this (our students do not have gmail and do not receive notifications of comments on google docs).
There are a few features that would enhance this tool that I would like to suggest:
1. If a teacher unsubmits a student's paper or project, the student should receive an automatic message to notify them of the 'un' submission. Otherwise, students are unaware that anything is wrong.
2. To go along with the first idea - when a teacher unsubmits a student's document or project, it remains "submitted" on the student's schoology page - another reason that students are unaware of a problem.