"Professional reviews" aren't completely unbiased. Apple has a way of punishing tech sites that bash or call them out on their quality.
That's why its generally in their best interest to give a rough overall review that gives minor criticism and overall praise.
Also when you review a product you do it based on the notion that if something is wrong with your unit it is not a widespread issue. (unless there have been widespread reports of the issue) You review it as if it's working fine. People may have seen the issue but ignored it thinking their unit was just defective.
You wouldn't give a bad review if your ipad arrived with a broken camera.
"The ipad air 2 is a great iPad except for it's non working camera."