From a quick read of the review, it seems CR downgraded the GV80 mostly because of poor predicted reliability. Clearly, they had no real data to go on, so they probably extrapolated survey data from other Genesis models. I'm wary of CR's methodology, since the sampling isn't random, and people who've had problems may be more likely to respond. Also, problems with one vehicle line don't necessarily translate to others. Also, poor owner ratings for a vehicle with relatively low sales will have more effect on the results.
Still, I think Genesis needs to take this seriously and do more to address reliability, especially how they and their dealers respond to owner complaints. Interestingly, Tesla owners tend to love their cars despite problems with panel fit, paint, and other build issues. That may be because Teslas are so different from other vehicles that owners are more forgiving.