I agree that the issue probably won't affect shots in the real world, but it could.

)from what I've read)The issue is not just restricted to using the LCD backlight, it can be affected by direct sunlight on the LCD as well.

if this is true, then if you set yourself up for a landscape shot, and the sun peeks out for a moment over your shoulder and affects exposure from what you set it up to be, with viewfinder covered and so on, it may become an annoyance sometimes.

I suppose any effect on exposure up to approx 0.7Ev from expectation, wouldn't be too annoying.
I've got lenses that differ this much between each other and I account for those differences.
eg. the Nikon 18-105VR underexposes by -0.7 without fail relative to all other lenses given the same exposure settings.
Knowing this, as a baseline setting to account for, is easy to do, and easily remembered.

Problem is when this exposure variation is unpredictable from moment to moment.

if Canon offers a service fix or replacement camera, you would be best off to take up the offer(and any other offers of compensation).