I've worked in varying stages of childcare, I'm not a parent but I know plenty of kids personally. It seems to be in most cases that the child starts eating just one or two things but this range will expand and while there are definitely obvious preferances they eat most things (often the parents et smug at this point) until around 3 when suddenly it's all plain pasta and chicken nuggets. I've seen that happen in so many families with various types of diets.

Even as a child myself, I had to eat what was put in front of me but didn't like most of it and would kick up a fuss about it on occasion. I'm not a picky eater at all now.

It does make sense. Kids need healthy food to grow so surely from an evolutionary standpoint it'd make more sense if they ate most things. Young animals aren't fussy are they?