I believe that DYS really strongly prefers to have two test scores in the application packet. I recommend that unless your child has produced something incredible (which is rare at age five, even in PG kids) that you stick to the two tests. It is my impression that they are more likely to accept just one test if you have other "data" in the form of a product showing the same sort of advancement that they'd pick up from the achievement test. So if your child hand wrote an amazing short story, composed original music and performed it on video, etc. You might go ahead and skip the achievement.
I think portfolio admission was more common before the specter of PG fraud loomed over the gifted community. Now they feel a need to have more "hard evidence" to support admission.
