Fair enough you were querying a common misconception.
Living in the country I use the analogy of rain falling on a roof being collected in a tank that is large enough for a heavy downpour. Divide the roof in two and feed the collected water into two separate tanks half the size of the original and they will still have the capacity to cope with a heavy downpour. All other things being equal.
The ability to accurately determine the volume in each tank is related to other factors, very little to do with the roof area used to collect the water.