This pertains to new batteries only.
I do know that with my D Cells, rechargable or not, (assumed new) as the weight increases so does the capacity.
I mean within the same class. Apples to apples, oranges to oranges (alkalines to alkalines, chemistry to chemistry etc)
Super lightweight D cells have little capacity, and my heaviest D cells do have the highest capacity.
Obviously, the more of the innards there are, the more ions they can pack.
But is weight a reasonably good measure of a new battery’s capacity comparing it to other batteries in the same class?