Corn Starch vs Potato Starch
They are interchangeable 1:1, with virtually no changes needed. There shouldn't be any difference in the final sauce except that the cornstarch thickened one will be a bit more opaque. If you substitute the other way (use potato starch instead of cornstarch) don't let it hard boil (not for safety reasons, just aesthetics). In what country was the recipe developed? Could the need for potato starch instead of corn starch in your recipe have to do with Passover rules?