The title gives a lot of this away - but there are a few points I particularly liked in the main text, especially:
if, for example, only novice users were tested, a large number of usability problems may have been revealed, but the test would not show which are the most severe and deserve the highest priority fixes. Expert results may highlight severe or unusual problems but miss problems that are fatal for novice users
Results can vary with 5, and get most errors - or one study with only 5 returned 35% of errors! 😧
I also find this interesting personally as it’s debunking Neilsen things, and I always thought Neilsen was basically usability God.