5.7" screen is HUGE. I wish someone would build phone with 3.5-4" screen. It's so handy to operate phone with a single hand.
It's on par with most other phones, which I agree is huge. Smaller would take a lot more work, so I'm okay with a larger first version.
If you've ever seen a tear down of the iPhone X for example the boards are actually stacked to maximize the space available for battery in the thin form.
https://www.ifixit.com/Teardown/iPhone+X+Teardown/98975#s182...