Supergroup milestone not showing in subgroup board / issue list

We're trying this structure:

Where milestones go at the company level, while issues / boards go at the team group level.

After adding a milestone at the top level, subgroup issue boards / lists are not able to filter by or assign to that milestone:

However, when going to the details page of an issue, lo and behold, we can now magically assign the issue to it:

Is this intentional? Cause the rest of the team finds it very confusing.