It sounds like the author may have faced a bad interviewer, but I’d be curious to see their feedback on the author so we get both sides.
As I comment each time: you’re not being asked to sort a million item array because it represents the job, you’re being asked to sort a million item array because I want to see how you think, how you solve problems, and how good your underlying CS fundamentals are.
Yes - that means regardless of seniority, I expect you to know CAP theorem. Sure, knowing CAP theorem does not imply you are a good engineer, but being a good engineer DOES imply you know CAP theorem.
The job will change from project to project, but the CS skills should carry through.