TComponent and its descendants have built-in automatic memory release technology. This is the concept of the owner responsible for the destruction of the object.
Unless you specifically change this technology, it will work for any descendants.
When creating a form, a reference to the owner's object is passed to the constructor. For the main form, it is an application object that runs until it receives a termination signal. Usually the main form sends such a signal when closing.
By default, all forms except the main one are simply hidden when closed, not released. This technology is not related to the technology of automatic release by the owner of the components belonging to it.