Separate method for a single line code? Or embed in the caller function?
I'm guessing that your boss's argument is that a well named function would make the code more readable, and I agree with that in general. I often do that myself even when the function contains a single line.

In this particular example I would not bother though. The comment above the json-call says the same thing as the function name would, and there are no obvious advantages to make a function for a single call.

So if your question is specifically for this example, then I agree with you - keep it as it is, but if you want a more general answer, then I agree with your boss.

For example - if this one-liner is something that you use in more than one place, i.e. if calling the "processKeyVal()" function in more than one place makes sense. Then I say you should make a function of it even if it would contain only one line of code.

Or to put it another way - it is not (always) the number of code lines that should determine if you make a separate function of a code snippet.