Added an answer as a comment was too short.
This is how it works: when you enter the datagrid and you press "New" you temporarly create a new item (an empty line). Normaly you won't notice this as the datagrid in the background is not refreshed. However when you go to menu item and retrieve a new list or refresh the list you will see the empty line. This is because the newEdit screen is still open, if you now press cancle in the newEdit screen the object wil be rolled back and if you refresh you datagrid you will notice that the empty line is gone as well.
The feature has been removed, since it was to easy to circumvent. It worked when you clicked a menu item or button, but not when a microflow triggered opening a new form, or you closed the tab, refreshed the page etc etc.