Yeah, 15 bits is still a long way from 256. That being said, a 15 bit key - if truly arbitarily chosen - is starting to get my attention.
... also gotta say, though, that a company whose business it is to sell security from quantum offering prizes for supposed proof of vulnerabilities to quantum does smell a bit sus on the surface. I would expect to see pretty soon an impartial analysis of what was actually accomplished here.
https://blog.projecteleven.com/posts/project-eleven-awards-1-btc-q-day-prize-for-largest-quantum-attack-on-elliptic-curve-cryptography-to-date
