This is a different mod from the extra screw at the end of the seat runner. It looks to me like they effectively fit an inertia type seat belt under the seat and fix it to the floor.
More info at
http://www.cessna.org/htmlatis/SEB07-5R2.pdf
I think this is what Pilot-DAR has seen.
Just-Local - already been through the seat belt shenanigans as well. Had a argument with our CAMO and he eventually rescinded (thanks to lots of PPRUNE input) . I recently discovered by accident (UPS contact me about a import duty charge) that they are sending other belts there now too.