Channel mapping in FFmpeg conversion of Dolby 7.1 mlp file to 8 channel wav file

Question

I have a mlp file with 7.1 audio with the following channel mapping (viewed using MediaInfo): L R C LFE Ls Rs Lb Rb

I want to convert it to an 8 channel riff64 wave file, so I'm using the following command:

ffmpeg.exe -i "input.mlp" -rf64 auto -c:a pcm_f32le "output.wav"

When I do this, the channel mapping in output.wav changes to (viewed using MediaInfo): L R C LFE Lb Rb Ls Rs

I'm not sure if this is just a label that gets slapped on there, or if it actually changes the channel positions (i.e., rear surround comes out of side surround speakers and vice versa).

Is there a better command I should be using to ensure that the channel mapping is not altered?