On the Food network they boil potatoes, but they poach carrots. They poach turkey, but they boil eggs. They sauté’ onions, but they fry eggs in the same pan. Likewise, they fry hash browns, but they sauté’ onions in the same pan before adding the potatoes.
I can go on for days.
It usually has to do with what chemical process happens to the food in question. Not all foods react the same to being dunked in boiling water. (Although I couldn’t tell you what the difference between potatoes in boiling water and carrots in boiling water.) In the case of onions vs eggs, the same process is 1) extracting the water and using it to make sauce, with the onions, or 2) boiling off a tiny amount of liquid and heating the proteins to solidify them, in the case of eggs. Same method, wildly different chemistry.
Sometimes it has to do with how long that cooking method is applied, since a different thing happens. For example, you can poach OR hard-boil an egg; same method, different amount of cooking time.
In short, with a few exceptions, it’s not about what process you’re applying to cook the food, but about the result that it achieves in the food item.
Poached and hard boiled eggs vary by more than just their cook time. These names are much less about chemical processes and more about differences in technique. See other comments in this thread.
If I hand you an egg and tell you it’s a poached egg, you’re going to thinking about the consistency of the egg, not how I cooked it. Poached means the result, not the process.
I mean… you get the result by doing the process. You can get different consistencies based on how long you cook them for.
They’re different techniques with different results. You can’t give me a boiled egg and say it was poached and have me not be able to tell. Nor vice-versa. You can have runny boiled eggs, you can have soft-boiled eggs, you can have hard-boiled eggs, but you can’t make a boiled egg look like a poached egg.
