Just want to add my 2 cents.. Can't ever see why we bother so much with banding on images that are 5-6 stops underexposed, but hey, going with the flow there are a couple of points that need correcting.
1. This is definitely NOT a Mirrorless problem as previously stated in these posts. Banding was evident in my father in law's Eos 1Dn II years back so lets get back to basics.
2. Canon Eos R are not exempt .
3. Too many reviewers are biased. We know that, so know real point getting on the pedestal to preach... Most of those early reviewers were only about getting their clicks on their websites, without having clearly had the time to offer any useful and meaningful knowledge on a camera that had been in their hands for barely a few days at the best. Not talking about Steve Perry btw.
4. Last but not least is that reviewers can very easily make a camera look poor as can others make it look really great. But what is really happening is probably 99/100 anything shown poorly now is really user error.