Requestors have no access to reports that are marked Share System Wide.
Requestor licenses are often used to grant access to users who don't belong to or are outside of a Workfront user's own company. Workfront doesn't want users to share objects system wide without realizing that Requester users will get access to the object and expose company data to users outside of their organization. To address that, Requestor licensed users are not include when Share System Wide access is selected for a report.
For future reference, using a "Company" in Sharing options instead of Share System Wide option would allow everyone in your company to see the reports.
No Requestor licensed users can access a System Wide shared report unless it is Shared another way with the user as well.