Does there have to be a board? Spyfall is no different to Imposter, except that there is no board, nor cards.
D&D is mentioned as a board game, but you don't really need a board.
Maybe we should call them "tabletop games" instead, in which case I think card games should make it (bridge, for example, means reading both your partner and your opponent).
The terms "board game" and "tabletop game" are considered pretty much interchangable by the vast majority of hobby board gamers, "board game" just tends to be the default. There's no requirement for a board game to have a board. BGG is full of card games, tabletop RPGs, dexterity games like jenga, junk art etc - none of which have boards
"Tabletop gaming" was a term invented specifically to capture things that weren't considered self-contained enough to be a "board game" or "card game".
I agree that "a board" is not necessary, but I do think that "less faff than D&D or Warhammer 40k" is a hard requirement.
D&D is mentioned as a board game, but you don't really need a board.
Maybe we should call them "tabletop games" instead, in which case I think card games should make it (bridge, for example, means reading both your partner and your opponent).