In the Requirements Coverage project tab : No sub-requirements found

The issue:
When a project contains only the sub-requirements (links based) the Requirement Coverage tab doesn't see them.

How to reproduce:
1. Create TCM project with a Change issue type
2. Create REQ project with a Requirement issue type
3. Map both issue types to Xray Requirements Issue Types
4. Set Requires/Required by Issue Link Type as a link between a Requirement and a Sub-Requirement
5. The Requirement Coverage tab on TCM project works fine
6. The Requirement Coverage tab on REQ project returns "No requirements found..."