[rickdeckard]

Depends on whether "expensive" refers to

a.) Compute-cycles: Some added passes to apply additional shading on top of the completed render, or

b.) Power-consumption: Some added delay in putting components to sleep (reducing CPU/GPU-clock) on every screen update.

Deferred sleep for a portable, battery-powered device because of a longer UI-rendering pipeline can easily add up over time.

--

I'd be quite interested to see some technical analysis on this (although more out of technical curiosity than the assumption that there is something huge to be uncovered here...).

There's also the aspect of iOS prioritizing GUI-rendering over other processing to maintain touch-responsiveness, fluidity, etc. Spending more xPU-time on the GUI potentially means less/later availability for other processes.

For sure non-native apps trying to emulate this look (i.e. Flutter) will create a significantly higher impact on the power-profile of a device than a native app.