It's not specific to Hondas.
The explanation I have for it is that regular gears are a helical cut gears while reverse is a straight cut gear, which lends itself to whirring noises. I believe the main reason for the noise is that it's a helical gear driving a straight-cut gear....and yadda yadda yadda, it whirs.
I'm sure I can get a more detailed description if you'd like.
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