@Herwig0I believe @Steve143 is correct in that a guest can leave 5 stars in each category but 4 stars overall and this then counts as 4 stars in your percentage, i.e. the 80% 5 star reviews you need to be a Superhost.
However, I am not sure if the category ratings do not count at all. From what I understand, these contribute to the overall rating, where I think you have to get 4.8 out of 5 for Superhost status. Airbnb has confirmed on the forums that Location does not count towards this rating though. I assume then that the other categories all do, but if anyone knows that this is wrong, please do correct me.
I had the same situation where a guest left a lovely review and 5 stars in every category but 4 overall. I could not understand why as she seemed to be so happy while she was here. So, I wrote her something like, "I see you left 5 stars in every category, so I just wondered if you could give me some feedback as to why you left 4 stars overall and which areas I could improve on..." She was very surpised as she said she meant to leave 5 and it must be a mistake!
So, I contacted Airbnb CS and they actually changed the review to 5 stars once the guest had confirmed that she did indeed intend to leave 5.
Of course, this would only work if your guest made a mistake, which I imagine is unusual.