Now you’re just shifting the goalpost.

You initially said beyond a surface level and now you’re talking about esoteric quirks.

Pick one. Of course nobody has the same definition as you if you’re shifting the line and simultaneously not defining what you mean.

You don’t need to know every aspect of a languages corners to be proficient in it. If that were true, there’s only a handful of people on this planet who’d be proficient in a single language let alone multiple.