TTLS Distance measurement

[iND]

When using a Canon 5d3 and an 680EXRT in a TTL mode and a lens that is capable of evaluating subject distance (which results in a flash compensation for subject distance)

Is the focus point the only determinate of the distance, which in the case of the 5D3 is the central focus point 100% of the time, and does the metering mode come into play. ( I know this answer may be different with 1Dx models).


A real life example is using TTL flash with a bride coming down the aisle. If the focus point is moved from center and the metering mode is expanded, does the center point still determine the distance and feed the information to the flash to recalibrate for a changing bride distance?

Thank you.