If you take a 20-deg. reflective reading up close, you should get the same result as if you take a 5-deg. reflective reading farther away of the same area. The only significant factor is the flash-to-subject distance.

To think of a more extreme case--in general the exposure for a floodlit building at night is about 1/4 sec. at f:2 at ISO 400. On a clear night it doesn't matter if you are standing across the street and photographing with a wide lens or a mile away and using a long lens. The only issue is the distance between the lights and the building. The exposure does not change.