This is an excellent question that I never thought of!
My guess is that
- there is a large range of cal concentrations that work fine without tasting bad, and
- the amount of water absorbed by the corn is very hard to predict, as it varies from batch to batch, and
- unlike brining meat, it is unlikely that two people doing this by hand would vary how much water they are adding by 5x or even 3x, because there is no reason to add a lot more water than is needed, and
- recipes are simpler if you base the cal amount on the corn amount and then add "enough water" (which may change once you start cooking).
So maybe no one doing it for non-industrial audiences has bothered narrowing it down.
I use around half as much as you (3:1 water to corn and 1% cal by weight of corn) and it works well for me.
My guess is that
- there is a large range of cal concentrations that work fine without tasting bad, and
- the amount of water absorbed by the corn is very hard to predict, as it varies from batch to batch, and
- unlike brining meat, it is unlikely that two people doing this by hand would vary how much water they are adding by 5x or even 3x, because there is no reason to add a lot more water than is needed, and
- recipes are simpler if you base the cal amount on the corn amount and then add "enough water" (which may change once you start cooking).
So maybe no one doing it for non-industrial audiences has bothered narrowing it down.
I use around half as much as you (3:1 water to corn and 1% cal by weight of corn) and it works well for me.