The "physics" I was referring to is simply that any angled blade being pulled through the soil has some degree of scraping going on at the bottom of the blade, similar to the scraping compaction at the bottom of a plow.  A concave disc has some other things going on at the base of the blade also.

The amount of scraping is related to the angle of the disc blades in relation to the direction of travel.   In a full width disc, essentially 100% of the width of the tool is subject to this scraping action.

Compaction is a very complex subject. In the OP, the tires just change the depth of operation.  If there is enough weight left on the blades to keep them at any consistent depth, the scraping action is still going on just at a different depth.

Jim at Dawn