The light Leak DOES affect the images. The faulty metering causes some images to be underexposed. Imagine a scene on the limit between two exposure levels. The light leak will then cause the scene to be exposed at the lower level. This will happen at ALL LIGHT LEVELS! Furthermore, in some situations, the light leaking onto the meter through the LCD screen will cause the image to be underexposed several steps. For example, I recently used a 10 stop ND grad to blur the water in a waterfall on a sunny day. In that situation, the sunlight leaking in through the screen is relatively large compared to the scene (as seen through the filter). The result was an image underexposed by many steps, and the images came out completely black. So the statement from Canon indicating that the leak does not affect the captured images is NOT TRUE..
Serious Light Leak Issue with the 5D mark III!
Light leaking trough top LCD causes underexposure