Unless you’re 7 ft tall, no ones body wants to weigh 315 lbs. it just doesn’t and no amount of pseudoscience is going to make that statement true. There’s so many different variables but off the top of my head, I bet if your diet was structured in a way that you covered your macronutrient needs in a more nutritious way, you’d likely have a hard time eating enough to get to that 3,000 kcal mark. You could, but it would take way more food than you think. If you’re eating calorically dense food with little nutritional value then no, it’s not hard to bang 3,000 kcals in a day but when it’s things like grilled chicken, lean steak, broccoli, rice, sweet potatoes sans butter and brown sugar it’s much harder.
But don’t get me wrong, by all means if you want to weigh that then go for it. I myself walk around at 320 and I’m pretty content. And it takes me at my activity level around 4,000-4,300 kcals a day to maintain this body weight.
There is some merit to the set point theory and not all people operate optimally at a low body fat. But to think a body that is say for instance 5’7 or so “wants” to be 315 lbs. as an optimal body weight is highly spurious.