Hello Vaibhav,
As per my knowledge When the root objects are fetched using the get_query_result( ) method, only that result will be in the buffer but not the related data. When you use get_related_entity then the request will be handled by the genil class which makes use of the root object data to fetch the related entity. Here it checks whether already the data is available in the buffer or not. If already this entity is fetched before from db then only this will be available in the buffer but we are fetching it for the first time using the get_related_entity so the genil class access the corresponding API which in turn fetches the data from DB and now this will be placed in the buffer so that next time when the same request comes then data can be fetched directly from the buffer.
Regards,
Bala.