I think part of this confusion stems from the "default mic on" mindset, where "mic active" is assumed to be the default, and mute is a deviation from that state. We can trace this pattern back to the UI of phone conference systems, back through analog phones, back to the time of a literal wire connection between parties.

Many/most audio mixers (in the context of live music and recording) and their digital brethren use the same pattern - a "Mute" button which lights red to indicate that channel is silenced. But a few have an ON button above the fader which lights to indicate the channel is active.

I think it's about time conference applications rip off the bandage and take the "audio off by default" approach. We can kinda see it already with UI elements that light up when a speaker is talking.