Canvas does not allow best practices in rubric use. Peer review is merely a scaffold to self review. Peer review teaches a student to grade a product with a judicious eye, and aquaints the students with the criteria on the rubric. But grading Suzy's paper doesn't tell Sam what to fix in his own paper.
A meta-analysis conducted by Black and Wiliams, published as "The Black Box," review 581 research papers and chapters on assessment and concluded that SELF REVIEW yields the greatest effective size in teaching students how to improve their own product.
This limitation on Canvas forces teachers back to pen and paper rubric evaluation. Considering that Canvas already has teacher rubric evaluation and peer rubric evaluation coding established, it should be fairly simple for Canvas to give the student to opportunity to grade himself.