Ive learned something quite different. I have a lot more water than bone.
The theory from what Ive learned:
As a Norwegian, the explanation might not make sense, but I will do my best to describe it in a reasonable manner.
As the stock simmers, it will end up absorbing flavour from the stock. At a point there will be the same amount of flavour in the bones and water. At this point the stock wont be able to absorb more flavour from the bones.
(The following is imaginary number I just use to explain in a more understandable way.)
If you to 1 kg of bones use 4 liters of water you will be able to get 60% of the potential flavour. If you use 6 liters of water instead, you might obtain 70% of the potential flavour.
As you probably all know, theres always the possibility of making a remoulage (second stock) on the same bones later, wich tells us there is always more flavour left in the bones after the first stock. It will of course not be as much as in the first stock, hence the 10% increase in flavour by adding more water. Adding more water is not a problem, because it will be reduced anyway, therefore not dilluting your final product. The only difference is a bit longer time needed to reduce it down to the 1 liter you would want in the end anyway.
You might even want to do a remoulage on the stock afterwards, to later combine the remoulage and first stock, before reducing it again, and by doing so obtaining 80% of the potential flavour.
If you want to make a simple experiment, make two cups of tea. Both with one teabag, but one cup with 1 dl of water, the other with 1,5dl of water. The ratio is the same as the 4/6 liter example earlier. The 1,5 dl cup of tea wont have a lot less flavour than the 1dl cup, but if both are reduced, to 0,1 dl, the 1,5 dl reduction will have a stronger taste.
I dont know if it makes sense to you, but through observing and trying both ways, I am convinced this this method is better.