How does vinegar let sushi rice stay near room temperature during service without constant refrigeration?

Answer: It makes the rice acidic enough that bacteria grow too slowly to matter during service

It makes the rice acidic enough that bacteria grow too slowly to matter during service ✓ — Correct! Sushi vinegar brings the rice down to a pH of about 4.6 or lower, and at that acidity the bacteria that worry food inspectors, such as Bacillus cereus and Clostridium perfringens, multiply very slowly. That is why food codes in many places let a restaurant hold acidified rice out of refrigeration for the service period, provided the vinegar is mixed in evenly, the pH is measured and recorded, and the rice is discarded after the set time. The acid slows growth; it does not sterilize the rice, so the time limit still matters.

It dries the rice surface so bacteria lack the moisture to grow — Vinegar is a liquid, and it adds moisture rather than removing it; fanning in a wooden tub cools the rice and takes off a little surface water, but sushi rice stays moist and glossy by design. Bacteria are held back by the acid, not by dryness.

It adds alcohol left over from fermentation that preserves the rice — Vinegar is made by fermenting alcohol, but by the time it is vinegar the alcohol is gone, turned into acetic acid. Nothing alcoholic reaches the rice, and food-safety rules for sushi rice talk only about acidity and measured pH.