I use
Scoop! to view metadata of all video and audio files. Knows all the formats and containers I have come across.
It is a front end to the same analyser library as
MediaInfo.
Try both.
Spotlight does index the Audio Bit Rate. Hence the data is available to Get Info, but it doesn't display it. You can do Finder searches with Audio Bit Rate:
But Finder does not display audio bit rate as a column. You need
HoudahSpot to search for audio bit rate and/or to display it as a column.