It seems that I can get a "Content" match of "100.0%" even for two files with different length and different bitrate. It is, I think, unreasonable - it is not the same content if it is not the same content (different tags are OK as long as tags are a separately-reported thing).
It might be that the Precise algorithm can tell the difference, but (1) then disclose that, although you like to keep the Precise algorithm a secret, and (2) deduplication based on audio content is an even less sophisticated method than the non-Premium mode; not only is it available in less sophisticated deduplicators, but from a user point of view it is counterintuitive to switch to the more sophisticated method to get a less sophisticated method.
Suggestion: For streams that decode to the truly bit-exact same signal, display "exact" rather than "100.0%". Takes the same space in the table.
(That does mean that you might need to round off decoded mp3s somewhere around -150 dB if you do not calculate with very high precision, if you do not want a CBR and a VBR with the same signal to be reported as different.)