Epic dates from milestones don't work when using /epic in a new issue

I just created an epic, &1367. To populate it, I created a series of new issues and assigned each of them to the epic, along with a milestone, by using quick actions:

/epic https://gitlab.com/groups/gitlab-org/-/epics/1367
/milestone %"12.2" 

I did this in the issue description. That did not calculate the start and due date for the epic: https://docs.gitlab.com/ee/user/group/epics/#start-date-and-due-date

To make the epic update the calculations, I had to remove and re-add one of the issues, then it worked correctly.