I think some kids are just more prone to gorging on 'treat' foods than others & some kids are greedier than others too.
My dc are young adults now but I saw this play out quite a bit both in my own childhood & when my dc were small
I grew up in a house where my mother had a very sweet tooth & we ALWAYS had a treat / snack cupboard. Because ir was always there & there were no real restrictions on it myself & my sibling weren't all that bothered with it
We regularly had chocolate 'leftovers' from Christmas, Easter, Halloween etc
My best friend from school came from a bigger family (5 kids) & her mother had a much more 'sensible' approach to stuff like this & they had very few, very restricted access to snacks or treats.
She loved coming to my house & would literally gorge herself to the point of stomach ache on chocolate / cake / biscuits. My mother worked & as young teens we were often there alone & i didn't care what she ate.
I have a vivid memory of her finding an old tin of roses & tucking into them. They were all the flavours we didn't like. I suggested she should check the best before date & i can still see the look of disbelief on her face that you could have chocolate so long it might have himself out of date! She ate them anyway & told me that she'd never heard of just leaving the ones that weren't your favourite. In her house they scrambled for their favourites & then just worked through the ones they didn't love as chocolate was chocolate!
She def had some eating/ binging issues as she moved from teens to early adulthood
Later when my dc had friends over after school or parties there were also kids who were VERY motivated by the food - constantly asking for food, or checking when it would be ready, declaring themselves starving & then often not eating much of the actual food in favour of stuffing themselves with whatever treats were offered.
These kids weren't following any particular restricted diet. They were just more interested in the goodies than some of the other kids who couldn't care less about the food & wanted to play.