For those of you that have been following the discussion, I've posted an example below of how the balance of light from the flash on the subject and background changes as the distance to the subject changes. Hopefully this will make more sense after I show the examples.
Couple about 1/3 of the way up the aisle (so not too far from the back of the church). (Focal length at 70mm) Light falloff between the subject and the background isn't too drastic.
Couple about 2/3 of the way up the aisle. (Focal length at 32mm) Light from the flash is lower power because the couple is closer, therefore less light from the flash illuminates the back of the church
Couple very near the front of the aisle (3 meters?) (Focal length at 28mm) Light from the flash is very low power because the couple is relatively close, therefore less light from the flash illuminates the back of the church
As I mentioned earlier, with a little pre-planning/visualization/testing the photographer could make a conscious decision of how far away to photograph the subject in order to capture a pleasing balance of light between the subject and the background. (Of course any prudent photographer would take several shots, just in case the couple blinked.) Personally, I like the middle shot the best.
I hope these examples help?
Keith