So only at the sdarim one needs pas naki not to change the mitzva? How does this explain that we “change the mitzva” at all other times when we dip in salt?
At the Seder, where the Matzah plays somewhat of a dominant role, we don’t want to “dilute it” with anything else. For example, the Matzoh is simple bread, adding salt takes away from its simplicity.
No matter what angle you take with the matzah, you want it to be just that, and nothing else.