I've been revisiting the viewport tag on MDN and in article Viewport width and screen width, they suggest:

Suppress the small zoom applied by many smartphones by setting the initial scale and minimum-scale values to 0.86. The result is horizontal scroll is suppressed in any orientation and the user can zoom in if they want to.

<meta name="viewport" content="width=device-width, initial-scale=0.86, maximum-scale=5.0, minimum-scale=0.86"

The MDN page was last modified on Jul 27, 2021. I've always used initial-scale:1 for my work and have never come across any mobile device which applies zoom to it.

1. Are there really many smartphones that apply zoom? If yes, please give a few examples.
2. Where does the number 0.86 come from? Any references?