Interesting! We did a similar analysis on Content Security Policy bugs in Chrome and Firefox some time ago, where the average bug-to-report time was around 3 years and 1 year, respectively.
https://www.usenix.org/conference/usenixsecurity23/presentat...
Our bug dataset was way smaller, though, as we had to pinpoint all bug introductions unfortunately. It's nice to see the Linux project uses proper "Fixes: " tags.