Peter -
This is due to safety.
Yes Radio Equipment is made to run in 10Khz spacing, BUT radios in bigger robots where their are parts causing interfearence, also some people dont use top quality servos - it makes it a problem with bots going out of control or not staying stil when being armed.

When robots are in the arena, the 10kHz gap does not matter, but in your case, a robot needed to be tech checked - which meant the robot is OUT SIDE the arena, more safety is needed- this is where the 10Khz rule came into play.

Mr Stu