Part of the 'explanation' in that article is that "in order to work, reflector needs to be under direct light, and it directs light right back. That means that if it is lit from the left side, it will reflect the light to the opposite side – to the right."
That would be correct if you were using a mirror as your reflector, but is not true at all for the 'corner reflector' technique used in actual reflectors. In these, the light is reflected back in the direction from which it came: i.e. if lit from the left side the light is reflected back to the same side, to the left. That makes reflectors far more effective than mirrors would be since the driver's headlight beam is directed right back at him even if it hits your reflector at an angle.

[You get the same effect if throwing a ball hard into the corner of a room (i.e. where two walls meet the ceiling or floor). After bouncing off all three surfaces the ball will rebound back towards you.]