To generate a PRISMA report with reasons, reviewers need to ensure that they have the Answer Level Agreement selected in their Level Settings.
DistillerSR does not track the reason for exclusion in Form or Question instances, only that the two reviewers agreed to exclude.
Optionally, you can enter custom reasons for exclusion by modifying the Exclusion Report directly in Reports > Exclusions and PRISMA. Clicking the italicized text "Click here to assign a label to this exclusion reason" to edit the text and enter custom reasons. These reasons will be outputted in your PRISMA report.