I respectfully disagree.  One of the worst things you can do in a moist seedbed is have a piece of metal dragging below the opener blades -- this 'firming point' does indeed pack and smear, but at the worst possible location: where the seed will be placed.  You don't want extreme compaction below the seed.  Makes it much more difficult for the root sprout (radicle) to penetrate this layer and move downward to continue to draw moisture.  Also, it makes it much more difficult to achieve seed-to-soil contact when the bottom of the furrow is smeared and compressed badly.

Firming points may have some merit in very dry loose soils (tilled), sandy soils, but they are a disaster in no-till or in any type of soil with clay & moisture in it at seeding time.