Meanwhile, the vast majority of people making calls are still going to have only one speaker, so it’ll still get downmixed to mono. Even if your phone has two, and you’re not holding it next to one ear, they’re still going to be so close together as to effectively be one point source.

No, lots of (probably most) phones and other devices has stereo speakers.

Either way headphones are most often used for this (you know like the thumbnail)