JSON Video bitrate, required?

For the ‘bitrate’ field, The JSON feed spec states:

The bitrate in kbps. For non-adaptive streams, this must be provided. It is not needed for an ABR (e.g., HLS) stream.

However, I’ve noticed that the developer portal will accept a json feed file that specifies 0 (zero) as the bitrate for an MP4 video. What effect, if any, will that have on the video playback? Or, any other aspect of the video?