The system records the speaker - always. There is no way to manually select which participant gets the attention for the recording. Therefore, if you need a particular participant to be highlighted, it is important that only that participant's mic be active -- all others must be muted -- otherwise you risk having unwanted participants continually popping up. Consider these two scenarios:
If you're PRESENTING YOUR SCREEN for an on-screen demonstration that is being recorded, if there are other participants, noise on their end could disrupt the image being recorded. The particpants could "pin" you so they aren't distracted, but the recording will be interrupted and future viewers will see the interruptions.
If you're hosting a video conference, and you want to add your mobile device as a remote camera, you must mute your speakers and mic on the host computer, and enable the speaker and mic (or headset/earpods) on the mobile device. This will ensure that the voice being "heard" is the mobile device, which allows this device to maintain the "focus" of the recording, so the proper image will be displayed on the recording.