You are confusing stereo with two channel audio. Two channel audio can work to create stereo, but it in itself is not stereo (rather two mono channels). Where stereo become stereo is when you position a sound in space, using panning to place it left or right
(a combination of panning, volume, HRTF filters and cross talk cancellation techniques can be used to simulate depth and height). If you hard pan a sound into either left or right, that sound is now mono, as it comes from a single source.
Stereo is the multi-dimensional illusion of space and direction of sound. Using two channels (left + right) and two speakers is the traditional method of creating stereo which is why so many confuse the two. Quadraphonic sound (four channels, four speakers) or even multi channel, multi speaker surround setups are all methods of achieving stereophonic sound.
A two channel, two speaker setup is the simplest, but also the most primitive way of achieving stereo. The more you move out of the sweet spot (think a equilateral triangle between your head and the speakers) the less effective the illusion becomes.
As Apple stated, their aim was to eliminate the sweet spot by making a consistent multi-dimensional experience regardless of your or the speaker’s position in the room. And by all reviewers judgment they’ve succeeded.
I’ve stopped following Dalrymple on most things, but he’s a musician and obsessed with audio, so I trust him on this:
It’s hard to explain the sound of HomePod, but you get a feeling that the sound is enveloping you, even when using just one speaker. There is a sense that this is how the songwriter and producer wanted the song to be heard when they recorded it.
The other speakers gave the feeling that music was just being blasted straight at me and not allowing me to become part of the experience. HomePod sounds great wherever you are in the room—there really is no particular sweet spot to hear the music, it just sounds great everywhere.
People get far too hung up on their belief in what stereo means based on their conditioning. This is fine, unless you want to argue that the HomePod is mono (or to a lesser extent “not true stereo”). By any definition it isn’t, and what truly matter is what it sounds and feels like when you listen to music on it.