My ex had one eye like that, she claimed it let her see in the dark
Maybe somewhat… It would let more light in, but it wouldn’t be focused correctly.
https://en.m.wikipedia.org/wiki/Polycoria
It results in decreased of the iris and pupil, affecting the physical eye and visualization.
When the iris becomes deformed, it will disarrange the control of light coming in leading to blurred vision and finding it hard to visually focus.
From what I’m finding it either has no effect or bad effects but never good effects like better night vision so you just got lied to or they said that as a joke and you didn’t get it.