Dates of subtasks are not being adjusted by my workflow
This will occur by default if the subtask is not attached to the project that's under Flowsana control. By default, Asana doesn't assign subtasks to the project of their parent task.
If you want to have subtasks which are not attached to their project participate in Flowsana's Dynamic Duration or Auto-Adjust workflows (or If-Then rules), you can do that by selecting the "Also apply this workflow to subtasks" checkbox when creating your workflow:
With this option selected, subtasks will be included in the workflow, regardless of whether or not they are attached to the workflow's project.