Summary

The "Create a sub-task" option is available in the issue view when the issue type is configured as a level above epic (Eg Initiative)

Expected Results

Hide/remove the "Create sub-task"  button from the issue view when the issue type is configured above an Epic in the Issue type hierarchy and prevent users to create subtasks in such issue types (often called Initiatives)

Actual Results

when an issue type is configured in the Issue type hierarchy above an Epic (eg. and initiative), it still shows the option to "Create a sub-task".

Workaround

Create a specific project that only contains the above Epic (or commonly Initiative) issue types as described in the documentation "Configuring hierarchy levels" under the section "Ways to set up the initiative level in plans"