The original paper is titled "Bipedalism and brain expansion explain human handedness". It doesn't seek to explain why we have a right-handed preference specifically (vs left-handed), but rather why humans have such a strong handedness preference compared to ancestors who had only a mild right-handed preference.
IOW, why handed vs ambidextrous, not so much why left-handed vs right-handed.
IOW, why handed vs ambidextrous, not so much why left-handed vs right-handed.