i don't think it's that asigmatism is itself an overstimulating thing. It sounds like their brain finds streaky lights overstimulating, and it just happens that they're coming from that source.
I have significant astigmatism & am not bothered by that.
It's more that each of us has specific things that our brains don't like. Ex. Some hate the feel of OJ with pulp. Some hate OJ without it. 🤷♀️