I'm no physicist, but if I remember correctly, light is some form of electromagnetic radiation, which means EMR travels at speed of light. In that case, it's not surprising that an electrostatic field can travel at similar speed.
From my understanding the quote is talking about electrostatic effects that occur when electrons move to fill a void/go away from a negatively charged area. Since the force that makes electrons repeal each other is very weak, I think it makes sense. But note that it mention "a single electron." Voltage deals with a difference in immense scales of electrons, so I assume the effect and speed would be different in practical cases.
From my understanding the quote is talking about electrostatic effects that occur when electrons move to fill a void/go away from a negatively charged area. Since the force that makes electrons repeal each other is very weak, I think it makes sense. But note that it mention "a single electron." Voltage deals with a difference in immense scales of electrons, so I assume the effect and speed would be different in practical cases.