Probably - the current implementation of that button seems a little counter-intuitive. Wouldn't it be better if the button represented the current state of the mic, ie. no-cross out when the mic is active but crossed out when the mic is muted, and not the other way around which is how it is now?

This would be consistent with the volume mute icon (the button for which doesn't currently work) - when the volume is at zero the speaker is crossed out (ie. it's currently inactive) but when the volume is > zero the speaker has no cross out. The phone app runs counter to this approach.