I can't stand this feature, because it overrides my OS-level choice. If I select my headset as the microphone to use, then I expect it to be used. But Zoom might use a different microphone, so I need to change it there as well.
In addition, even if I select "System default microphone", that doesn't always work correctly. As far as I can tell, that option doesn't mean to attach to the default source. Instead, it means to attach to the same source that is currently bound to the default source. If I change the default source later, Zoom doesn't get moved along with it.