I feel like this is a reasonable response. Early childhood is an easier time to regulate sugar intake and definitely developmentally crucial so you don't want any extra unhealthy foods complicating things.

I was raised similarly and have a pretty healthy relationship with sugar today. I just always worried about the kids whose parents freaked out about them having a soda at a birthday party when they were like 8 or something. I understand policing sugar up to maybe grade school, but past that definitely has a negative effect emotionally and can lead to kids bingeing when they're cut loose.