I have a series 4 and 24, why would I need a 9/10?

I had an interview last week with a brokerage firm for a branch position. One of the managers saw I have a series 4 and 24, and said thats nice, we don't need that; we need someone with a 9/10. I know the 9/10 has a municipal bond component to it, but really isn't a 4/24 better than the 9/10? And wouldn't a series 9/10 manager have to be ultimately supervised by a series 4/24? So why would they rather me have a 9/10, unless he just didn't understand the difference?