In rubrics, "Add level" button isn't appropriately styled

Test in Classic and Boost. As teacher, add a assignment to your course. In the form section "Grade" → "Grading method", choose "Rubric" and click "Save and display". Click "Define new grading form from scratch". On the rubric definition user interface verify the "Add level" buttons does look good (right hand side examples) and have the plus sign. Verify the "Add criterion" button does look good, too.