Hide unused users from assignee dropdown when using restrictive filter

[Marine Redon]

I created quick filters for teams in my organisation, e.g. 'Art team', which uses the following query: 

assignee in ("Name1", "Name2", "NameX")

Previously, when using a filter with a list of users, the assignee dropdown on the active sprint board would only display users matching the filter query. It doesn't do this anymore, it displays every single user on the project, even with the filter active. Is this a bug or is there a setting I'm missing somewhere? 

This is making it unnecessarily harder to pick people in team meetings. We have to scroll through a long list of users to find the relevant ones.