Although MJPEG may have a more stable and higher temporally local average bitrate, it's bitrate can vary widely given the input content. See MJPEG Compression
; the assertion that the resulting network frames/packets will be more consistent is totally unsubstantiated. It may be, at a macro level, given, say a 10Mb/s Ku Band spotbeam satellite transponder, MJPEG may actually simulate a HARD MUXRATE function that the MPEG Transport Stream muxer typically would perform, but even this is questionable, given MJPEG's highly variable bitrate given very simple content.
Hard Muxrate: https://stackoverflow.com/questions/44392689/ffmpeg-vbr-cbr-conversion-and-streaming-of-mpeg-2-ts-video-files