When logged into Moodle, create a Feedback activity in a course. Next create a new group and add a student here and also a non-editing teacher we will be using.
Next, login as the student and take the feedback activity.
Now on the mobile app, login as the non editing teacher and click on the feedback activity. The submitted answers displays no red rectangle with the number of submitted answers.
If you click Analysis (2nd tab) the submitted answers then appear as white font in the red rectangle. you can then click back to the Overview tab and the submitted answers preview is present/remains. If you leave the feedback activity on the mobile app and then navigate back inside, it's as if it resets and you must click on the Analysis tab again in order for this result preview to be shown.
To my knowledge this is happening only for non-editing teachers.
I tested this on a specific Moodle app and the core Moodle app version 3.5.2.