From what I can gather, what we call breakfast 'only' goes back to Victorian times. Before that, it was quite different.
If you go to a place like Fairfax House in York (when it opens again!) around Christmas, they set up a period breakfast. It has all sorts of stuff like pies, cold meats, cheese etc plus bread rolls, toast, jam and so on. There might be eggs, I think. More like what we'd call a Continental Breakfast really. Jane Austen used to have toast and jam, hot chocolate and pound cake. Cake for breakfast!
Further back, it might have been pease pudding or some kind of porridge. And, during my daughter's stay in Nepal, they had dhal for breakfast every morning. Can't think many of us would associate curry with brekkie. Although kedgeree...
Don't know when (or where) the book was set. I've noticed US books tend to mention steak for breakfast more often. Isn't steak cheaper over there due to farming methods? As for when, if it's on a farm, steak might have been a cheaper option at the time. (Like oysters very often figure in older recipes because they were a cheap way of bulking out pies.)
Apologies if that's a bit swotty...