I was wondering, what does it mean?
What I mean is phrasing that makes allusions. You'll find it in writing as a tool to expand meaning, change tone, add connotation, etc. It can lose power and clarity when the reader is unfamiliar with the underlying references.
Here, the writing brings in an aerodynamics concept (coffin corner), a famous bit of psychology about cognitive biases (Dunning Kruger), and a trueism about doubting one's own capacity (imposter syndrome).
Personally, the reference to coffin corner adds richness to the writing. It is from a completely different discipline, less commonly referenced in HN context than the other two, and immediately gives me a sense of greater breadth about the author's experiences.