I believe that snakes learn to recognise smells and sounds and become accustomed to them. Snake behaviour is very simple there is directed and instinct.

The directed behaviour is exploring and investigating the type that you see having a snake out being handled.

feeding is instinctive behaviour, nobody home upstairs. Entering feeding mode requires set of triggers, smell, need, security, on and on. If they are not present the animal will simply not enter feeding mode. Some species enter feeding mode very fast some don't royals don't. I don't think it is necessary with royals to feed in a separate container. I also don't feel that unless you have some trigger present that a royal would enter feeding mode just by opening a door. I have some seriously aggressive feeders but have never had even so much as a strike position on anything other than feeding evening.

The scent of rat in the air and the vibrations of the hair dryer and opening seem to be enough trigger for mine. I often do water bowls while rats are thawing and have never been struck even then. I have been when I forgot the ziplock baggie that had last nights meal on top of an enclosure the next evening during a spot clean however. Scent, heat, movement, vibration these are clear triggers.