Here is the complete contents of a newly opened Revell-ogram Galaxie stocker chassis kit: (minus 2 screws stuck to the other side of one of the magnets)

To me the "chassis" is strictly the big slab of plastic at the top, and I never had any intention to use any of the extra bits below which I don't consider part of the "chassis".
From the photos you posted I think what you're calling "axle holders" would be more clearly labelled as "bushing mounts"? In most cases the bushing mounts are part of the chassis structure, except in the front of the Revell-ogram chassis where a separate block has the bushing mounts. I already cut off the mounting posts for that block in the front of my chassis, because my resin body has places to attach front bushing mounts directly to the body.