My immediate reaction when I saw this was "gimmick." Actually it sounds pretty clever, if it works I'll use them.https://cyclingtips.com/2021/04/vittoria-announces-run-flat-foam-tire-inserts-for-road-bikes/
These go between the rim and tire, on road tubeless systems. The air pressure within the tire compresses the foam, and, supposedly, it doesn't touch the contact patch when the tire is inflated - which means it doesn't add any rolling resistance. Is the claim.
If your tire gets cut beyond what the sealant can handle, you lose air pressure and the foam expands. You can ride about 50k on the foam without damaging your rim.
Tubeless systems rarely flat, but it's usually harder to get the tire off the rim when they do.