That is interesting, huh, yeah they list ffmpeg as a dependency so I wonder what that didn’t cover for them.
Though there are some cases where using pure ffmpeg is just to difficult or impossible. Recently i had such a case where I wanted to merge multiple video files from my GoPro (they come out in 4GB parts if the video is longer than that), but while keeping / correctly merging all metadata such as date / accelerometer / gps / any custom binary streams. Ended up using this and worked great https://github.com/gyroflow/mp4-merge
Though there are some cases where using pure ffmpeg is just to difficult or impossible. Recently i had such a case where I wanted to merge multiple video files from my GoPro (they come out in 4GB parts if the video is longer than that), but while keeping / correctly merging all metadata such as date / accelerometer / gps / any custom binary streams. Ended up using this and worked great https://github.com/gyroflow/mp4-merge