SpeedGrader should continue to show submission details whether the assignment is anonymous or not. Instructors at our institution need to be able to see when assignments were submitted in SpeedGrader while they're grading anonymously so they can adjust their grades accordingly.
The current behavior in SpeedGrader is to hide submission details for graders when anonymous grading is turned on for an assignment. This page documents that behavior. If you have an admin role you can still view the submission details. This behavior should be preserved for users with the teacher role or other roles with grading permissions.