All tasks, including start tasks should have form configuration defined in this way, they will be shown in both view (task details page) and edit (edit task page) modes so that should be considered when defining forms. As shown above the new info.ftl form control can be used to display metadata on an edit form but in an 'informational' way i.e. not in a disabled form control!
The easiest way to solve your problem:
define your custom .ftl file based on default ftl. For example, try to modify hidden.ftl
after that use your control in config file to describe the fields that you going to hide: