The engineer will just have you do an autorotation RPM check anyway. The 206 is about as benign a helicopter as you can find in autorotation, and a prudent pilot would get plenty of altitude before entering anyway, and pay attention to the RPM and start a power recovery before the RPM gets out of the green. I've never seen the Nr in a 206 dangerously low with the collective full down, and they have lots of blade inertia.