I have interviewed two "senior web developers" with "10+ years" of experience that were unable to tell me the difference between a 404 and 500 http response code. Of course, they had perfectly memorized answers about JavaScript closures.
Presumably, programmers who are working with the web should have a passing familiarity with the most common categories; this isn't memorizing all of them, but being able to recognize the significance of 2xx vs 3xx vs 4xx vs 5xx codes isn't an unreasonable expectation.
Web developers spend most of their time in javascript - coding fronted where closures and functional programming matters a lot. Maintennable modern fronted is done that way.
They spend very little time staring at http error codes. Like, none.
