Issues from subprojects assigned to a top level group iteration are not shown in that iteration

Summary

Issues do not appear on iterations as expected (e.g. the way they do with milestones with the same hierarchy).

Steps to reproduce

  1. Create an iteration at the top level of a multi-level group (e.g. Products > Product Name > Product Project)
  2. Assign an issue in the project in the project in the subgroup to the iteration
  3. View the iteration - no issues are shown

This bug does not occur if the iteration is on the subgroup, only if it's on a group up one (or more?) level.

Gitlab EE v13.2.1

Example Project

Iterations were not available in the project I tried to set up on Gitlab.com.

What is the current bug behavior?

No issues are shown, despite being assigned to that iteration.

What is the expected correct behavior?

I should see all issues in all subprojects that are assigned to that iteration (like milestones do).

Relevant logs and/or screenshots

Screen_Shot_2020-07-29_at_11.14.53_AM

Screen_Shot_2020-07-29_at_11.15.36_AM

Output of checks

Unable to test on Gitlab.com

Results of GitLab environment info

Unclear how this is relevant.

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)