I truly think that you hit the nail on the head here. My views on birth were a lot different in my first few years of midwifery training. It wasn't until I had been to over 110 births that I saw some very scary complications. It was quiet sobering and made me feel that my previous "trust birth" stance was very naive. I think Dr. Amy brings up some points that need to be addressed by the NCB and home birth community, but that her overall approach brings shame upon herself and the bitter gossips that follow her.
Any OB/GYN resident working in a busy teaching hospital will see 20 to 40 deliveries per week. 1000 babies in 5 years sounds perfectly plausible to me.
It's possible that this gap in experience between OB/GYNs and many homebirth midwives is part of where the gap in understanding comes from. To someone who has only delivered 40 or 50 babies ever, a "1 in 500" chance might sound low. To someone who has delivered a thousand babies, "1 in 500" translates directly to 2 dead babies and 2 grieving mothers that you've seen with your own eyes, and is a situation you must be prepared for.