OP, I think you posted in time to get the late night trolls then the MN orthorexics came in.
3 square meals is fine if they're decent portions and balanced to keep you going from one meal to the next. This is not what OP's parents provided.
Snacking culture has become more informal, but has always existed to some degree. Elevenses, a biscuit with a morning cuppa, milk, tuck at beak time, something to eat when getting home from school, supper... a lot of people never lived soley on 3 meals with no snacks at all, but it was often more structured than today.
At my school in the late 80s/ early 90s we had a tuck shop selling small bags of crisps or chocolate. Things like Tangy Toms, Fish and Chips or Freddos. So yes, there was an established snack culture. Other families I knew at the time did have some kind of structured eating between main meals. DH growing up in a poorer country in the 70s/ 80s came home to home made soup to fill up on, and had deserts made from produce of the garden.
DM was a war child and spent her youth being rationed, then younger adult years in the 60s/ 70s with waife-like aspirations. By my 80s childhood she was battling middle-aged hormones and resorted to diets like The Cambridge Diet. She was a penis portioner too.
Fortunately for me, I didn't have a huge appetite until my teenage years. I spent 13-15 being perpetually hungry. I did get away with secretly making myself second dinner of beans on toast after dinner. Fortunately she didn't pay too much attention to the loaves of bread missing a couple of slices and didn't eat beans much herself. She would never have believed that I needed so much extra food and would have been full of dire warnings about getting fat. She regularly went on about another female and her appetite and weight.
Going to uni and buying food for myself was great. Fortunately I liked cooking fresh food for myself, and the novelty of sweet treats wore off before any damage was done and I've remained a healthy weight and build through adulthood.
What OP describes is a lack of understanding of her needs and a relationship where she hasn't been able to get those needs met. That's both physical and emotional. That can very easily result in a disordered approach to healthy eating and confused boundaries in the long run. Working that out can help to build healthier habits and self-love.
From OP's age, it sounds unlikely that her parents would have experienced rationing themselves and were more likely young in the 60s/ 70s. They sound mean-minded rather than purely growing up in difficult circumstances and repeating the cycle despite changed circumstances.