Yeah, that's because there's an entire cottage industry of people scraping old bug reports, and linter errors to create CVEs they can sell to customers worrying about security. It creates a huge number of false positives. E.g. see https://daniel.haxx.se/blog/2023/08/26/cve-2020-19909-is-everything-that-is-wrong-with-cves/

I think any measure that is looking at a raw count is going to be meaningless. Particularly, comparing raw counts between open and closed software.