I installed the Soft Seal door weatherstrips and they are now hollow, you can't tell (visually) from the appearance however they "crush" much more than the old Soft Seal.
The biggest difference other than the fact they are not latex covered foam are in the ends, the original has a stamped metal plate molded in where it attaches to the door the Soft Seal does not, they have flat washers installed in those places.
I am not 100% sure however I believe the OER Latex Foam WS I installed in the last car did have metal plates.