But my question is still appropriate. Assuming strong loads and favorable payload data, would it be conceivable that a row of seats be added to generate a little more revenue if the fuel burn is less than expected?
Revenue does not equate to profit. Putting another row of Economy seats will not increase profit margins. The associated costs and ticket price per seat of an extra row of economy will not increase profits. It will however decrease passenger seat space, crew work areas/galley space, perhaps even reduce toilets. That extra row of seats has to come at the expense of other space. An aircraft fuselage/cabin is a finite space. The profits come from the Business and Premium Eco seats. In summary, the extra row/cost of Eco might provide 'revenue' but will not provide a 'relative' profit.
Actually, it would increase profit (or decrease loss) if they can fill the seats in this case. The plane is already lightly configured, so adding a single row would decrease the pitch so slightly over the entire economy cabin that it wouldn't even be noticeable. In this case, it would not require reducing toilets, crew areas, etc. Again, I mentioned 1 extra row of seating, not 4 or 5.
If the seats can be filled, it would require very little airfare to cover the cost of installing them and hauling those extra people (fuel, catering, etc), thus, making nearly all the extra revenue profit.