Ours has expanded metal baskets in it.  I have been told that later models did not, and that it was recommended to discard the ones in ours.  There is no way I would discard them.   They help stop problems and I don't really see what the downside is. 

I could see where excessive air could be a concern with seeding, especially with delicate seeds.   Blowing fertilizer and seed at the same time would pose a bit of a challenge.