I believe that means the v8 sandbox, not a renderer sandbox, based on the v8CTF reference.

Then what it was chained to is the real issue, not this one. The entire point of having webpages run in their own process is to prevent bugs like this one from doing worse. If you're claiming this bug is the bug that matters, you're effectively claiming they shouldn't need to run pages in their own process and just trust that there are zero bugs. No major browser does that. Not Firefox, not Safari, and not Chromium.

that's why bugs in the webpage process pay out very little. Without a worse 2nd bug, they are less serious. Bugs that let you RCE outside the webpage process pay much higher.