It seems to me that the term 'chair' also covers armchairs, and it should be accepted.
''lourd'' means heavy, ''gros'' means large, big.
A gold bar is ''lourd'' but not ''gros'' and a Pillow is ''gros'' but not 'lourd''
What is the difference between armchair and chair? the chair is heavy. Should be accepted
Fauteuil large chairs, upholstered, with substantial arms, the kind of chairs you would put in your salon or living room.
So, les fauteils are a subset of les chaises. "Chair", being a much more general term, is a very poor translation of fauteil. In my opinion, it should not be accepted.
"Armchair", however, looks to be identical to fauteil.
Some images of fauteil: