Necessary on occasions but not quite sure why. Must be very awkward with all the controls facing away from the direction of travel with the driver needing to be constantly facing them and the fireman busily shovelling. Is there a third man in the cab these days acting as a lookout, assigned to stand facing the direction of travel?
You've made two false assumptions, which are what is confusing you.
1. Visibility is obstructed in either direction on a steam loco. Team work in sighting signals is essential in either direction. Firemen are required to assist in keeping a look out, and must be disengaged from physically firing when necessary to do so. There is far, far more to firing a loco than just shovelling rock; the latter is not a continuous process rather.
2. Drivers do not need to be facing controls, or constantly hands on with them. Easy enough to adjust something when you need to. Driving trains is a totally different concept to road vehicles.
Any limits imposed on tender first running are due to the suitability of the tender itself for being propelled. Propelling a train is a totally different matter to tender first running, which was/ is perfectly normal and acceptable on low speed lines. You'll see it every day on the Esk Valley, come the summer months.