There's about a 100 posts in this thread now where we're basically splitting hairs over definitions of stereo.
My take: traditional stereo sound requires 2 speakers spread some distance apart with the listener positioned roughly in between the two, such that right channel sound coming from the right speaker hits the right ear and left channel sound from the left speaker hits the left ear.
Take a jumbo roll of toilet paper and set it on some counter. Imagine it is this product. The only way you can get in between the multiple speakers of this product is if you could squeeze yourself inside the cylinder... or maybe shrink enough to sit atop the roll.
Yes, there are technological tricks creating faux stereo or even faux surround. Bounce "beamed" audio off a right wall and bounce another "beam" of audio off a left wall and you can faux it, perhaps even reasonably fooling ears into perceiving something that sounds more like stereo. See Soundbars for example- where left, center and right audio might be as close together as 3 feet. Some Soundbars will even claim surround sound with no surrounding (rear) speakers through such faux surround technical trickery/magic.
Even Apple themselves are encouraging those seeking Stereo sound to buy TWO of these. Yet about half the posts seem to be ignoring Apple's own words by continuing to try to imply that one can yield stereo.
Full circle: define stereo. If your definition is the traditional one I shared above, it's probably most likely you have to heed Apple's suggestion and buy 2 of them, spread them out some from each other and position yourself in between the 2 HomePods. If you want to split hairs, bend the traditional definition to fit some purchasing motivation or marketing messaging objective, etc., you might be able to claim just one of these is stereo and/or surround sound too.
Someone offered that iDevices are stereo with their 2 speakers. Conceptually & technically, I agree because there are 2 distinct speakers left & right and some space between them. But one needs to be able to approx. sit IN the Lightning port to get the traditional kind of stereo to which I personally subscribe. So Marketing can spin "Stereo" speakers without outright lying but none of us can probably shrink ourselves small enough to actually get in between those 2 closely-positioned speakers to get a real stereo experience.
Same here. If you are AntMan or similar, you might be able to sit on top of a HomePod, effectively getting yourself between the multiple speakers in this thing. However, if you are full-sized human, real stereo will likely take 2, magical beamforming spin or not. Before someone takes offense at that, note that Apple says it takes two HomePods too.