Can app users be assigned as task assignees when starting a pre-configured workflow?

Specifically, I need to understand:

1. If an app user or service account starts a pre-configured workflow through the API (POST /workflows/{workflow_id}/start)
2. Can they add another app user as a task assignee at the time of starting this workflow?

I've checked the Box Developer Documentation but couldn't find specific information about this capability. Any documentation references or real-world experience would be helpful.

Thank you in advance for your help!