I think this is sort of half true. He did evolve once he started getting the complexity of nen however if he is like pitou then even in his most basic form he probably had a more than ok grasp of nen in general. Take pitou for instance. Her first fight was against kite, a high level nen user. This was the first time pitou had used his powers, if anything his first fight ever. And his volume of power was easily enough to overwhelm that other ant that had learned nen and easily defeat someone that had been doing the whole nen thingy for his entire life. The implication here of course would be that the royals, on the second they were born, had a good grasp of nen in general, they could use it to an extent instinctively and they could overwhelm high level nen users with ease. All royals evolved as they fought however the main aspect which was improved seemed to be their specific techniques. In turn things like ken and perhaps ryu seemed to come naturally to them.Take pitou when she first faced netero. She was using her en and in an instant she withdrew it and changed to attack mode. This is actually pretty advanced nen usage, even among high level nen users we have seen we rarely see this level of skill. Being "born" with this ability to move around nen is extremely significant and pretty much means the royals are not only born with superior nen volume as others but also superior skill is inherent to them. And as the manga advanced they even mastered their hatsu. Pitou got a grasp of his 3 dolls, youpi got a better grasp of his transformation ability.
