god, I have a 12 mini and I don't know what I'm going to do when it dies. my attempts at finding a vaguely modern name-brand android phone that's a similar size have concluded in zero phones and a sense of overwhelming dread
Same, on a 12 Mini right now, been looking for phones (any OS) that has similar size for maybe the last 2 years, and while some Xperia models have come close to the right size, everyone is still aiming for "bigger === better" it seems. Can't wait for the pendulum to switch back to smaller phones again...
This is totally not "vaguely modern name-brand" but I've been using the e-ink Mudita Kompakt and it's more or less the same size, but a bit thicker. It's Android but no Google Play Services but probably doesn't tick your box
You're comparing wrong models though? X9 and X300 Pro are both much larger than the phones I mentioned.
(I've just noticed you also used wrong models in your original comparison - while both phones are larger than the mini, the difference isn't as large as your link suggests)
The iPhone is normal phone size width and depth, but it's meaningfully shorter than just about everything else. It doesn't sound like much on paper but I've always found it adds up once in a pocket. (All dimensions height x width x depth, in mm, rounded up to the nearest mm)
In fact, they're more like the size of the full size iPhone, which, if you're sticking with your iPhone Mini because the iPhone is annoyingly large, means they're too large.