Can pianists write for organ?

Richard Elliot, principal organist at the Tabernacle, told me just how excited the full-time organists were when Ryan Murphy took the job at Temple Square. Why? Because he's a real organist. Apparently, he supported himself during grad school as a choir-director-organist at some Christian denomination or other in Boston. So, every Sunday, he was playing the organ WHILE directing the choir. That ain't easy. Richard said they were excited to play his music because he could empathize with them...