I can understand wanting stay anonymous; many companies are hostile towards people who find security vulnerabilities. If they have a real vulnerability and share it I'd accept their request to stay anonymous.
If they would not share until I paid, or did something sketchy other than requesting anonymity then I would probably consider it more on the hostile side, but not just because they didn't want to share their true name.
If they would not share until I paid, or did something sketchy other than requesting anonymity then I would probably consider it more on the hostile side, but not just because they didn't want to share their true name.