I actually liked the questions because if you spend enough time writing web apps, I feel you will run into all of these situations, e.g. manipulating argumentsI've been writing code for web sites since the web was a new thing, and I don't remember ever writing code that used the arguments pseudo-array in JavaScript. I'm sure I've probably used plenty of tools that relied on arguments for their implementations, but not reinventing wheels and all that.
I tend to think these kinds of questions are almost as flawed as brain teasers if you're trying to hire someone who's actually any good at programming. A long time ago, when I first started programming professionally and only used one main language, I was quite the language lawyer and new all kinds of arcane tricks. Today, I often look up how to find the length of a string/array/list/vector because I'm not sure whether it's x.length, x.size(), len(x), or any of another half-dozen variations that are used in different programming languages I know. I usually do get it right, but experience tells me it's faster to check anyway than to wait for a Lint tool to run or a compilation to fail if not.
Knowing the concepts in each language is important, so you know what to look up. If a JS developer doesn't understand what "this" means or how prototypes work, and by extension they don't have some awareness of why you'd need to use "call" or "apply", they might struggle. But we have IDEs and search engines and automatic style checking tools and all that good stuff today, and there are more important things to remember than details I really can and do look up in seconds when I need them from time to time.
The way I see it, asking an obviously experienced developer how many little details of a specific language they can remember is rather like asking them to take a typing speed test. In theory, the result might tell you something about how fast they can get work done, but in practice you're unlikely to learn anything very useful because the result won't be strongly correlated with writing good code that gets the job done well.