Yeah, I liked that explanation. It's still pretty sloppy of the episode writer, but you came in with a nice save. And yeah, I can see Khan's arrogance make him decide he's "above" such observances. In the book I believe he shaved and ditched the turban after the chemical accident in India.I don't remember that, but I did write those books some thirty years ago, so my memory is fuzzy. I do remember that I dealt with Khan being a very atypical Sikh by having him decide, grandly, that the old rules didn't apply to a genetically-engineered superhuman such as himself.
Which, honestly, seemed very in character for him. On the TV episode, only Marla labels him a Sikh. Khan never refers to himself in those terms; instead he proudly identifies as a superior specimen of (super)humanity. That's how he defines himself, not as a Sikh.
I don't recall Khan being a title myself. In the novel that was his name.