...I'm assuming you mean achieve 25% lye concentration by increasing the amount of water and not by reducing the amount of KOH...
Yes. Varying lye concentration only changes the water weight. It changes nothing else.
If you left the lye concentration at, say, 25% and then increased the superfat, it is true your alkali weight would be reduced but you would also see the water weight would also be reduced to keep the lye concentration at 25% based on the new, reduced alkali weight.
For those who might be wondering what we're talking about, here is more info --
When designing a soap recipe, you first decide what fats you want, the percentages (or weights) of each fat, and the total weight of fat. You also decide what lye discount (often called superfat) that you want in the recipe.
Next, you calculate the amount of alkali (KOH, NaOH, etc.) For a given blend and weight of fats, the alkali weight can be altered by changing the superfat. With all other things staying the same, this is what changing the lye discount (superfat) does --
More superfat --> less alkali.
Less superfat --> more alkali.
Once the fat blend, fat weight, and superfat are set and your alkali weight is calculated, the last thing to calculate is the water weight. You alter the water weight by changing the lye concentration (or water:lye ratio).
Higher lye concentration --> less water in proportion to the alkali.
Lower lye concentration --> more water in proportion to the alkali.
Water is the last thing calculated once the other factors are set regarding fats and alkali. Hope this helps.