Or perfectionistic tendencies? My DS scored 0 points on his written test because he did not put pronouns in his sentences. He also capitalized his "b" so they didn't count it. When I asked him about the pronouns, he said he didn't think they were needed to get the meaning across. When I asked him about the "B" being capitalized he said he couldn't remember which way the little "b" faced so he made it "big" so they would know what he was saying. Also he is very VS. When he reads he leaves out all those pronouns and little words. He scores very high in Comprehension which seems to go hand-in-hand with his leaving out those "little" words in his written work.
I am on board with the VS and perfectionistic tendencies for a logical explanation.