All someone needs is a minute to get exposed. The 15 minute guideline is to limit exposure criteria to someone likely to have actually caught something. So while being exposed in passing means it’s possible to have gotten infected, it’s considered unlikely.
I used to think so, but my understanding now is that because of viral loads it is unlikely to catch it in a minute - it takes a larger dose of virus in order to get infected, especially with aerosolized transmission without direct droplet exchange, though it is by all means still possible to catch it in a minute.