[thaumasiotes]

> It is a different thing to use that language to understand completely scientific/medical/law/tax forms and texts.

Jargon has to be learned independently. This is true of every kind of jargon, not just academic and legal stuff. If you want to talk to junkies and sound like one of them, you'll have to learn how first.

The technical term for this kind of concern is usually "register", as in "writing in an academic register".

A Chinese college student once asked me to review a paper of theirs for English quality, because their professor had criticized the English in a prior paper and they trusted me to be a native speaker (which I am). But being a native speaker didn't really help; once I saw the paper, I had to say "I'm sorry, but I don't have academic business training; I can't guarantee that anything I said would be phrased correctly."