Which (late spoiler alert) actually explains anon's apparent misunderstanding. The master developed as Elliott's protector, and that alter would naturally need to be avoidant while also being high functioning.

I thought it was one of the better Hollywood portrayals of DID, actually, at least from my understanding of the condition. He's not violent like the characters in "Split" or "Identity", just like the vast majority of DID sufferers, and the roots of his behavior are tied to his childhood sexual trauma where DID tragically originates most of the time.