Feedback on feedback

I am constantly amazed by some of the feedback customers give.
Broadly speaking feedback can be split into three groups - 1 Ordinary sensible feedback - which is by far the biggest group 2 Nasty unfair feedback feedback - which is the one that receives most attention on this forum 3 Then there is the feedback where the buyer cannot seem to criticise the seller under any circumstances
I came across this one just now. The buyer gives 4 stars and made this comment:-
This book arrived promptly but the final chapter has been ripped out. This is very disappointing. …
How can you give 4 stars for a book with a missing chapter??? It’s a bit like Tony Hancock’s “The missing page”
This type of feedback is very common and , in my opinion, gives the lie to the idea that people only give feedback when they are unhappy.