There was no bug to fix, the PM didn't keep up with developments in an (apparently) core dependency and was passing outdated arguments to ffmpeg. The fix was for the project to update how it was passing flags to ffmpeg. They'd rather spend the time opening a ticket on ffmpeg's bugtracker and spend thousands of company money begging ffmpeg to help them, when MS is a massive corporation, is apparently relying on ffmpeg, yet has hitherto established no support relationship and also has developed no internal expertise on ffmpeg

They easily could have opened up the code and looked around to find the problem, or checked the changelog since an update broke it, or just rolled back to the last-known working version until they had time to figure it out, instead they just dumped it on ffmpeg's doorstep like their hair was on fire. FFMPEG's development model is explicitly that they iterate quickly and there are very likely to be poorly documented breaking changes between versions. It's not one you pull a new version of casually.