I owned an iPhone 13 mini. Basically the perfect small phone if there ever was one.
The downsides are extensive and the upsides are few.
- Battery life sucked. Since a phone is a 3D object making it bigger substantially increases battery capacity. It also makes packaging difficult especially if the goal is a flagship-quality phone. Good luck fitting in good hardware with a lot of features.
- Eyestrain. It’s small.
- Typing. It sucks. The phone is small.
And it turns out the upside of one-handed operation is limited. A simple PopSocket or OhSnap! will make large phones easy to use in one hand.
Plus, if pocketability is your issue, you can buy a folding phone like a Motorola Razr and still get a nice big screen when you pull it out.