Great question! Currently, as you suggested, directly changing a form's status from published to draft for deletion won't delete the form. We recognize this limitation and have actually captured this need in Idea# 88621, which you can track for future updates.
As a workaround, many clients choose to rename their forms to clearly indicate they should not be used. Some common labels besides "Delete," "Ignore," or "Do not use,", "Inactive," "Obsolete," or "Archived." These tags help ensure that the forms are easily identifiable and avoided during regular operations.
