Brew Ratio - Pour Over v. Espresso

So we got Espresso Brew Ratio from weight of dry coffee ground to the weight of liquid espresso in the cup.
For pourover, if we were to aim for 1:16 brew ratio, do we

  1. measure the amount(g) of water we pour over the coffee ground, with no regards to the retention and resulting final beverage weight
  2. measure the amount(g) of resulting beverage weight to the coffee ground?

Understand most of us go with (1), but why though? if we are doing (2) for espresso and call that “brew ratio”.

IMPORTANT: Please search the site for an existing conversation. Duplicates are boring, and wasteful.