Only the cheap clone receivers can be reconfigured for high channel numbers. Futaba does not have the engineering expertise to develop such technology.
You can use the 6108/6208 to configure your s.bus servos. You connect the servo to the channel number you want it to become (1-8) and boot with the bind plug. To program the servo for high channel numbers you switch to "Mode B" with the button. This is only to set the channel number of an s.bus servo and has no effect on the RX or PWM channel behavior.