> Could they not have upstreamed those features in the first place?
Hard to say without being there, but in my experience it's very easy to end up in "we'll just patch this thing quickly for this use case" to applying a bunch of hacks in various places and then ending up with an out of sync fork. As a developer I've been there many times.
It's a big step to go from patching one specific company internal use case to contributing a feature that works for every user of ffmpeg and will be accepted upstream.
I've also had that experience of patching an OSS project internally, with the best intention of upstreaming externally-useful improvements in the future (when allowed).
However, my interpretation of the article was that they did a lot more than just patching pieces. They, perhaps, could have taken a much earlier opportunity to work with the core maintainers of ffmpeg to help define its direction and integrate improvements, rather than having to assist a significant overhaul now (years later).