I somewhat agree with this. If the vulnerability is severe enough that it would allow them to drain all the coins, then why bother with the 50k reward?
Still, this does allow them to find multiple minor bugs in one go so I think it's still worth it. Plus, it improves customer confidence.
They are watching for hackers. This exploits potential hackers because CB is tracking anyone who tries to hack to get the $50,000.
Well, let's just all hope that $50,000 is good enough for the hackers to share the vulnerabilities they found rather than exploit those for themselves.