Fair. The scene was probably functionally there to introduce Katie speaking Japanese more than anything, but maybe they could have picked a better word to do that with.

Yes, all part of the fabric.

That's what I'm talking about - language skill isn't necessarily global. One can speak very proficiently about a specialist area and not be able to make small talk; for me the script is plausible.

I'm an ESOL teacher and I can tell you, speakers of other languages are often very capable of speaking at length and in detail about their specialism, but can't always tell you what the weather is or what they're wearing. Or order politely in restaurants.