What isolation keeps and what it drops
The technique favours centred content, which in a conventional mix is the lead voice — but also the bass, the kick and anything else placed in the middle. Instruments panned to the sides drop away most, so a wide arrangement isolates far better than a narrow one. The audible signature of the process is a slightly hollow, filtered quality, because you are keeping a subset of the frequency and stereo content rather than an unprocessed recording. That is acceptable for reference and study, and worth checking carefully before using in a finished piece.