The current default branch in GitLab is 8.x-1.x. This means any issue forks are branched from this version which is not the current recommended version on Drupal.org (which is 2.0.x).
Go to GitLab and look at the branches and see that 8.x-1.x is the default branch.
Make 2.0.x the default branch in GitLab.
Active
2.0
Miscellaneous
Hmmm interestingly the issue fork on this very issue says "Create issue fork with new branch from 2.0.x". Not sure how that's working but even so the GitLab default branch still ought to be set to 2.0.x!!