I'd guess Prime Video heavily relies on ffmpeg, then you got Elastic Transcode and the Elemental Video Services. Probably Cloudfront also has special things for streaming that rely on ffmpeg.
The "kill it with an email" probably means that whoever said this is afraid that some usecase there wouldn't stand up to an audit by the usual patent troll mothercluckers. The patents surrounding video are so complex, old and plentiful that I'd assume full compliance is outright impossible.
AWS MediaConvert as well which is a huge API (in surface it covers) which is under Elemental but is kinda it's own thing - willing to bet (though I don't know) that that is ffmpeg somewhere underneath.
The API manual for it is nearly 4000 pages and it can do insane stuff[1].
I had to use it at last job(TM), it's not terrible API wise.
The "kill it with an email" probably means that whoever said this is afraid that some usecase there wouldn't stand up to an audit by the usual patent troll mothercluckers. The patents surrounding video are so complex, old and plentiful that I'd assume full compliance is outright impossible.