When I'm curious about the bit rate of a given MP3, I can't find it on Mac. It's easy to find in Windows: Properties > Details (screen shot) but on Mac Comand>Info only shows the 'Sample rate' which is not the same. (2nd and 3rd screenshots)
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.