It’s not that simple. Aerodynamic drag is made up of surface drag and induced drag. Given the same coefficient of drag, drag goes up as S-wet goes up (which is what you’re referencing). Induced drag is a consequence of how much structure is required to create a flying vehicle. IF (and it’s a big if) the BWB turns out to be more structurally efficient, then the total drag for the plane might be less than for a conventional design.

(Source: I have an aerospace engineering degree from Embry-Riddle)