Nested Fragment model is not getting published on publishing Content Fragment

As par Adobe documentation, "If you publish a content fragment for which the model has not yet been published, a selection list will indicate this and the model will be published with the fragment" but the nested content fragment (created using Fragment Reference data type) model is not getting published when we publish content fragment. Is it a product bug or OOTB behavior.

https://experienceleague.adobe.com/docs/experience-manager-65/assets/content-fragments/content-fragments-managing.html?lang=en#publishing-and-referencing-a-fragment