My instructor is very good, and, and as such, he knows his strengths and weaknesses as a teacher. He tells me that he thinks that arm styling *could* become a great, great asset of mine - on the other hand, if done improperly, my arms could become a huge, lanky liability. He can teach me the basic things, sure, but he believes that there are other people out there who could take me further than he can with it, and he thinks he'd not be doing his job properly if he didn't let me know that (not unlike a family physician referring someone to a cardiologist if there is a need for heart surgery, no?).
I certainly don't expect that any single teacher is going to be able to give me my entire dance education, and getting coaching from a specialist not only can give me exposure to various other styles/techniques, but that exposure perhaps might be something that my intructor can benefit from too (like other professionals who consult with each other, and who get continuing education in their fields).
I hope that my initial query didn't give the impression that my instructor is incompetent - he isn't!