What B2 vocabulary is for
B2 is the level that opens doors: French citizenship, most French universities, and a good number of jobs. The Framework describes it as interacting fluently enough that a conversation with a native speaker costs neither of you any effort.
The vocabulary stops being about your life and starts being about the world. Le communiqué de presse, la présomption d'innocence, la désertification and l'économie collaborative are the words of somebody reading a newspaper, not ordering a coffee.
Precision is the B2 skill
At B2 you stop needing more words and start needing the exact one. Le fleuve and la rivière both come out as river in English, but a fleuve runs to the sea and a rivière runs into another river. The Seine is a fleuve. An examiner notices which one you picked.
Register works the same way. Souligner, affirmer and chuchoter are three ways of saying something, and the wrong one changes the meaning of the whole sentence. This is where the deck spends most of its cards.
Where these words show up in the DELF B2 and the TCF
The DELF B2 writing paper asks for an argued text: a letter to a newspaper, a formal complaint, an article. Connectors and reporting verbs carry it, which is why souligner and il convient de noter que are on this list.
The oral is a defence of a position built from a short press article, so press vocabulary is not optional. Le communiqué de presse and la présomption d'innocence are the language of the documents you will be handed on the day.