Why not the same? If you impose the restriction on competitors to use only the fuel that he/she has stored, it would be very unfair to allow one player to break this rule and refill himself.
Water isn't an energy source, though. Letting the robot top off on, say, hydraulic fluid or coolant or whatever, might be the same. Even battery water.
Yes, for brevity sake. Anyway, banning "fuels" but allowing other types of refills is a slippery slope. Can a machine have maintenance if it breaks? If no, can a human player be treated by a doctor if he has a muscle spasm?
