Searching for a specific Parent Link issue doesn't consider it's subtasks

Background

When searching for Parent Link, Jira/JPO searches for the CONCEPT or Parent Link, considering "Parent Link" is not EMPTY:

• Issues (subtasks) with parent issues
• Issues with Epics
• Issues with Parent Links (the JPO custom field itself)

The issue

If instead of the is not EMPTY clause we specify an Issue as Parent Link, Jira/JPO fails to consider the subtasks's parents as it had previously on the is not EMPTY search:

It should have brought 2 issues whose Epic is K1-7 and the K1-10 which is a subtask of K1-7.