Sounds like a threat to me. ffmpeg is a tiny team and Google is a goliath. Not to mention Google has used their AI to spam the same threat, about 8 times in the last few months https://ffmpeg.org/security.html
There is a lot of historical context with this sort of thing that has lead to systems like this that has nothing to do with google.
Besides google did not sign an NDA, they aren't under any obligation to keep anything secret. 90 days is a courtesy. They are fully within their rights to just publish their findings immediately if they felt like it.
If you don't then your users should have the right know, so they can decide for themselves whether or not the risk is worth it.
Do you think that just because a project doesn't disclose something it goes away, or that if google can find the bug that much better funded groups like the NSA or malware vendors can't. Shoving things under the rug is the worst outcome.
