Eating at maintenence is to maintain your bodyweight (which is the total of fat+lbm). If you maintain your bodyfat and increase LBM as you are suggesting, then you are not doing maintenence. You are doing a body re-composition. i.e. you are changing the composition of your lbm to fat ratio.

In order to grow lbm, you need to be in caloric excess. You cannot control nutrient partionining. I.e. you cannot control to which destination your body will send ingested calories. But you can optomise those cals for lbm growth with proper nutrient timing.

And yes, i read the other thread

Eat at maintenece and don't lift/exercise I bet you wont maintain your bodyweight

What if you gain a few inches on your height

You still have to eat in caloric excess to grow. If someone is malnutritioned, not likely they will reach their max growth before their growth spurt ends. Where is the body supposed to get energy to grow? You cannot grow on Love and Fresh Air alone. You need to ...

Why are there are so many growing kids that are obese? because they eat more cals than they require to grow. Thus making them fat. On the other side, there are teenagers that can eat a whole horse and still remain skinny. Such a person may not put on much fat if they are not eating too many cals. So eventually it comes down to cals in/cals out (in addition to genetics..etc).