I’d guess that charging phones overnight is a general smartphone thing, not just iPhones. It’s not that iPhones take all night to charge, but it’s the most convenient time to do it since people aren’t using their phones while they’re sleeping. iPhone 8 and X both support fast charging like you describe, but only if you get a more powerful charger than the standard 5 watt charger Apple includes with iPhones, which will get you close to a 50% charge in 60min. Still, what you’re saying is something I could’ve/should’ve included in my post, since the spread of fast charging is another thing that makes it unnecessary to have a big smartphone battery.