That’s a good point, but I’d have to see if that just pertains to the inside surface of the vessel, or also to the surfaces of the rock, etc. in the tank. Decades ago, I ran some tests to measure the amount of water trapped between the interstices of aquarium substrate (for more accurate tank volume calculations). I used different sized gravel in a graduate cylinder, then measured the water it took to fill the cylinder. I was surprised to see that the water volume trapped in the interstices was about 30% of the gravel volume, and it didn’t vary much with grain size until you got really far apart, like sand versus pebbles.
Surface area for biological processes isn’t much of a limiting factor in aquariums as they are normally run.
I was giving this some more thought. I can't readily think in metric, so I made a real world scenario using English units -
Two aquariums;
one is 20" x 10" tall x 10" wide. That holds around 8.65 US gallons. The inside glass area is 800 square inches. That gives a ratio of 0.011 gallons per square inch of glass area, or 92 square inches of glass per gallon of volume..
The next tank is 48" long by 20" tall by 12" wide. It holds 49.9 US gallons of water. The area of the glass is 2976 square inches. That gives a ratio of 0.0168 gallons per square inch of glass area, or 59.6 square inches of glass per gallon of water - so actually in the other direction of how I understood your comment - there is MORE water volume per wetted surface in a larger tank than a smaller one.