Technically, one might also argue something weird like, "If I can see sunlight, it's still daytime" in which case a different phenomina would come into play:
What this all comes down to is, roughly speaking, even after the sun has technically set, there's still a bit of leeway before we no longer see the sun/sunlight due additional factors.
For anyone wanting to know a bit more about why this is, here's some additional details:
https://www.youtube.com/watch?v=-sj868IzNrk
https://en.wikipedia.org/wiki/Atmospheric_refraction
Technically, one might also argue something weird like, "If I can see sunlight, it's still daytime" in which case a different phenomina would come into play:
https://www.atoptics.co.uk/highsky/zod1.htm
https://en.wikipedia.org/wiki/Zodiacal_light
What this all comes down to is, roughly speaking, even after the sun has technically set, there's still a bit of leeway before we no longer see the sun/sunlight due additional factors.