If polygon A shares a partial boundary of a larger polygon B, but is otherwise completely inside polygon B, turf.area() will give a different result for the dissolved result of A and B than B alone.

turf.area(turf.dissolve(A,B)) != turf.area(B)

This can be fixed by running turf.cleanCoords() on the dissolved polygon, at least in initial testing. I will put up an Observable notebook for testing soon.