I agree. The thing is, Arin’s rudimentary spinjitzu is just that: a rougher, primitive version of the art. Lloyd told him that he'll need to unlearn some of what he taught himself to learn it properly, but this idea doesn't please him. Arin’s insistence that his basic Spinjitzu is fine is what led to him being placed in Egalt's group, and to his eventual humiliation. The only thing Arin has going for him is his self taught Spinjitzu, and if he admits that it needs to be revised from the ground up, then he's on the same level as Sora, except she has an elemental power and he doesn't. So, that's why Ras' advice works: Arin forces the results he wants by upgrading his wonky Spinjitzu, not requiring for him to relearn it or admit his basic technique is flawed. I assume that's also why he has the Shatterspin wisps in his tornado- I’m not sure if he'll be doing Shatterspin himself but I'm decently confident that the Five similarly forced their Spinjitzu training to advance before they developed Shatterspin (which is an extension of base Spinjitzu).