The size of the files here are big enough that bandwidth is more important than latency. And by default it will only happen when the phone is plugged in and connected to wifi.
"By connecting your phone to the Internet—not just through apps and notifications, but at every corner of the operating system [...]"
And mistaken assumptions such as this one:
“When iOS started development and Android started development, that was 10 years ago. Networks were much slower, Wi-Fi was much less ubiquitous, and AWS hadn’t democratized cloud to the extent that it has, right? So because of that, a lot of choices were made that result in user pain points today, which could actually be alleviated by leveraging the cloud in the way we’re doing.”
Guess what, WiFi still isn't ubiquitous for 90%+ of the population that uses smartphones, and probably won't be anytime soon (think 3rd world countries, rural areas, etc.)
The creators must be aware of these concerns. I'd be interested in hearing their thoughts on the issue.