I have bad myopia (around -5) both my parents have it too and to me it has always been evident that it isn't purely genetic. I think I could willfuly downgrade my vision if I concentrated.
Assuming such an effect really exists, I expect it would be very difficult to statistically distinguish from straight heredity. Kids' early childhood habits tend to reflect family culture.
It's well beyond a genetic predisposition, it was a genetic guarantee for me.
How is this any different from a youtuber claiming the earth is flat or vaccines cause autism?