They have to be heavier since they look a lot like insulation as well. I don't believe these are used for bearing. They are most likely designed to span to the bearing points of the structure below and are strictly for forming purposes.
They look like they are used for the bearing of the slabs for the seating sections. There would be a lot more rebar in a traditional construction wouldn't there? The at the very least get rid of any unsupported spans in the slabs.