I think the videos speak for themselves...modern sensors, including canons, offer far more DYNAMIC range than 7-8 stops.
May be true, I haven't actually done any subjective tests of how many stops the files actually contains, I have just compared different cameras to eachother and see I sometimes get problems when I push shadows etc. The actual number is not too important, the relative differences are though. What the camera can record in a scene which then can be compressed into a print without visible noise.
The raw files are 14 bit, meaning that 14 stops down the signal is either 0 or 1. At 13 stops down, the range is 0 - 4. Quite coarse quantization. I would be suprised if those last stops are usuable.
The videos are interesting, but I would certainly not use lightroom as some base to check how many stops (the actual number) there are in there, since you can't really trust that program's linearity, so I'd take the "13 or 14 stops of useful dynamic range" with a grain of salt. How much visible noise and dead colors you accept is also subjective, and it also dependent on the picture what works.