Comment 4 for bug 1817896

Logically you are correct. Practically is a different story. 25 mils was most likely chosen because that is the smallest reasonable grid size that you can use and still ensure that you can connect to the pins in the schematic editor. Grid sizes 10, 5, 2, and 1 mils are going to cause issues unless you are incredibly careful when placing pins. Change this at your own peril. I'm reasonably sure that there will be a bug report about not being able to connect a wire to a symbol pin not long after this change is made. Once wire snapping is implemented in the schematic editor during v6 development, this issue goes away so I am tempted to leave this alone until then.