IIUC the theory is that the clients using native IPFS will be caching the content for a period of time and serving it to other IPFS clients. Therefore the load should be shared across viewers leading to a minimal increase on "origin" load.
Yes, theoretically that's the goal. Given they're showing 160GB of transfer on their servers, it doesn't seem like that's working particularly effectively. Regardless, this implementation does not demonstrate at all that IPFS would save a site from an internet hug -- just that Cloudflare can.