No, not really. Mythos found 3 CVEs, not 271.
https://www.flyingpenguin.com/mythos-mystery-in-mozilla-numb...
I think you're confusing CVEs and vulnerabilities here? Mozilla (per their longstanding practice) grouped multiple vulnerabilities found internally under a small number of CVEs.
The Mozilla team responded to that argument here: https://hacks.mozilla.org/2026/05/behind-the-scenes-hardenin... - in the FAQ.