No, what is happening is that as I will assume you know, 5.1 tracks are in the order of L,R,C,LFE, SL, SR. If you import any 5.1 audio track, this is the order they will appear in the channels on the clip from top to bottom. If I don't natively include the SL and SR on a timeline and then export, Premiere mixes the original L, R, and 4th track (What is traditionally the LFE channel, regardless whether Premiere has one or not) and uses that mix to create both the SL and SR channels on its own. So if you import the track back into Premiere, this is what you see in the audio channels regardless of you choosing to only export 4 tracks. You have 2 added tracks which Premiere interpolated on its own.
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