I think you are spot on with that observation. There may be personalities more or less suited to the task, but practice and determination will make most anyone proficient at calling a show if they want to do it. I agree, too, that getting the chance to do it, to face the cold fear or the giddy excitement head on, is the biggest challenge for those of us who really have a hunger to do this crazy job. That's where school can be a Godsend. I was thrown in to the deep end of the pond in my second semester in the Theater department at my community college. They needed an SM. I had non-theatrical management experience, but was TERRIFIED of calling a show. Woke up nights from nightmares of having brought the show to a crashing halt because of some blunder in my calling it.
I did make some mistakes in that first production. There were a couple of calls in that show that I NEVER got right and my LX saved my butt every time. These days there are still call sequences that I struggle with, calls I occasionally miss, but I have several small plays lined up over the next few months and directors calling to discuss scheduling future productions. Every one is a little easier, but even the small ones seem to keep the luster of the first one. I love my job.
Owen