Upcoming & Overdue Section Not Showing When Using Apex Class Data Provider

[jack-bennett-osf]

When I create a timeline configuration to be used on a Case record, where Task is a child object referencing an Apex Class Data Provider, I don't see the Upcoming & Overdue section.

The Upcoming & Overdue section appears when creating a child object configuration that is not referencing Apex: This is the configuration (note the Overdue field set to ActivityDate, which is the Due Date field):

This is what appears when I am using an Apex Class Data Provider (note: no Upcoming & Overdue section):

This is the configuration (note: Due Date field still configured):

We have two configurations for Task the use Apex Class Data Providers. One that gets Tasks of Type "Call", then one that gets all other Tasks. The above is just referencing one of those configurations. There are no other major differences other than the class reference.

Is there anything I am missing here? I can't see anywhere else in the config or Apex where I could ensure this works correctly.