The function of the primary phase (as in US politics and probably elsewhere) is to narrow down the field to a manageable set of candidates for final election. Since the field had only 9 candidates, that wasn't necessary; the SE software passes up to 10 candidates to the last phase anyway:
After 7 days, the top 30 nominees, ordered by reputation, advance to the primary phase. However, if there are 10 or fewer candidates, we skip directly to the election phase.
The primary's secondary function is to give more time to campaign with the questionnaire and so forth, but (at present) that's just a side effect, not a deliberately-supported function, and SE does not yet have any provision for that effect if there are fewer than 11 nominees.