I would have wondered but the footnote of my NA (Wordsworth Classics ) told me the Rumsford was a modern fireplace designed by Benjamin Thomson ,Count Rumsford to minimise smoking fires.

I believe Count Rumsford was also very critical of English kitchens which he considered pretty archaic in the late C18th.
Rumsford fireplaces were used for heating and cooking.

Interesting site on Rumsfords.
i'm sure General Tilney thought himself a great renovator. Yet I see him as rather authoritive and traditional in his attitudes.