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).