Why would a device require at least 10m of wire between its outlet and the service panel?
To limit the maximum current and voltage in the event of a short circuit.

Extra resistance between the power source and a surge protector limits the maximum peak voltage to the protected equipment. That was good advice.

Close to the breaker panel, the available short-circuit current is considerably more than at the end of a long run of wire. The resistance and the inductance of longer wires sometimes matters. 

Years ago, I helped wire a commercial building. All the wire had been pulled, and all that was left was to install the duplex receptacles. Well, I  started at the farthest point --at least 75 feet-- from the service entrance. Not knowing which breaker fed what, to shut off the power to each box I simply shorted the wires together to trip the breaker.

Well, that worked very well, until I came to a box that was only a few feet from the panel. When I shorted those wires, the current was so large that the flash temporarily blinded me. When I regained my sight several seconds later, I realized that my gloves were on fire. It did trip the 20A breaker; but when I reset it, I could tell from the feel that the contacts inside the breaker had arced and were nearly welded together.

Here's an excerpt from a Littelfuse PDF.


  The apparent 'clamping' of the voltage results from the increased
  voltage drop (IR) in the source impedance due to the increased
  current. It should be clearly understood that the device depends on
  the source impedance to produce the clamping. One is seeing a voltage
  divider action at work, where the ratio of the divider is not constant
  but changes. However, if the source impedance is very low, then the
  ratio is low. The suppressor cannot be effective with zero source
  impedance (Figure 2) and works best when the voltage divider action
  can be implemented.


The longer the wires that ultimately power the surge supressor, the greater the source impedance. And the greater the source impedance, the lower the surge voltage will be at the protected equipment.