Different mute indicators for CarPlay and iPhone

Is there a reason why the active mute indicator is different between CarPlay and iPhone? The iPhone active mute indicator is a button with a white background and a red icon whereas the CarPlay active mute indicator is a button with a white background and black icon.

We make a CallKit app that supports CarPlay and that's how this was noticed, however the Apple phone app behaves the same. I suspect this is intentional as to cut down on distractions for drivers.

Any further explanation would be appreciated.

Thanks

Different mute indicators for CarPlay and iPhone
 
 
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