I have created Task list on O365 and a site content type of Workflow Task (SharePoint 2013) . Added this content type to Task list. When I tried to create a workflow on this list and using "Assign a Task", it only shows default content type in "Content Type" dropdownlist but not the newly created custom content type.
Yes, I did create a new task list and also added couple of site content types (Workflow Task SharePoint 2013 as parent content type). Still not getting any custom content types added to the task list.
I have also found this issue today. We have the content types available on both the list with the workflow, and the workflow task list, but the only content type available is "Workflow Task (SharePoint 2013)".