Mendix considers autocommitted objects a modelling error, from the documentation:
" If you end up with autocommited objects, it is always because of a modeling error. At some point in time, an association was set to a new object, the associated object was committed, and all of its associations were committed as well to keep all the data consistent."
From this point of view, it makes sense to not commit them, since they would persist the result of a modelling error.