They absolutely didn't.
I don't get how there seems to be absolutely no human side to these cases.
Guy discovers critical vulnerability and could have completely fucked the company over. Instead he responsibly reports it, and he gets back a big fuck you. How can you possibly think that's fair? The fact that it's out of scope only means they should give him an out of scope reward - much higher!
Saying he could have not checked the credentials is a bit silly, because if the credentials were invalid (quite likely), it goes from CRITICAL to MINOR.
And isn't the entire point in bug bounties to encourage pen testers to explore your system? Sure, you don't really want them poking around your source control, but better that than black hats.
All of the above aside. They really couldn't spare $500 for someone who could have caused $millions of damage?