IMO, I think you're spending more time talking about edge cases than the norm. How many people are web developers vs those developing web browsers?

Understanding query cost has more to do with data structures than algorithms. Why does the optimizer seek vs scan? What column(s) do I need to index and how should it be structured? You really don't need to understand how things get sorted in a b-tree.

Knowing normal forms is also different from algorithms. Ergo, it would be more useful to ask "When would you denormalized your data?" instead of "What's the difference between Quicksort and Bubble Sort?"

Objective-C is really just one of many languages I know and use. It just happens to be the most recent. Oddly enough I did spend some time (many years ago) implementing my own browser for a job. We used Java and, again, I never really had to know the complexities of sorting algorithms.