Thanks for reaching out. Unfortunately, this is a known issue and there isn’t a great workaround. I’ve taken your request to our API team.
I’m not certain of your exact desired workflow, but here are some characteristics of ‘user’s tasks lists’ that you may find helpful in creating a workaround. All user task lists are projects in Asana. They all have the same name: “My Tasks in Asana, Inc”, the team is “null”, and the project’s only follower is the task list user.
Sorry we don’t have a better solution for you at this time.