Cannot get Active Tasks which are part of a subprocess

I have a parent.bpmn which has a CallActivity within it, this Call Activity is attached to a BPMN (lets name it child.bpmn). When I am trying to start a process instance I am able to do it, I am able to get the processInstanceId as well. My very first task in the parent bpmn is CallActivity so as soon as i start my BPMN the execution goes into CallActivity, and halts at UserTask, now in a different point of time, I am trying to get the active task details, but i get the size to be 0, i tried getting the active tasks with child definition key and business key (always unique in my case).
Attaching Parent and Child BPMN.

When I go to the cockpit and see, the token is at call activity of parent bpmn, when i go the called instances then i get to see the token at user task of child bpmn, which is correct, however when i query for active tasks, i do not get anything.
When querying for process instances, I am getting correct result:

processEngine.runtimeService.createProcessInstanceQuery().processInstanceBusinessKey(applicationNumber).processDefinitionKey("APFlow").active().list().size

here is how i am querying TaskService to get active tasks: for both i am getting zero
ChildBPMN.bpmn (4.2 KB)
ParentBPMN.bpmn (2.9 KB)

processEngine.taskService.createTaskQuery().processDefinitionKey("ChildBPMN").processInstanceBusinessKey(applicationNumber).active().list().size


processEngine.taskService.createTaskQuery().processDefinitionKey("ChildBPMN").processInstanceBusinessKey(applicationNumber).active().list().size