I not sure that photo from where, that photo actually do show the burn-in button of home and recent.

Just the person draw that red indicator is kind of dumb, it is like pointing to the line showing the navigation bar color but in actual is point to that two burn-in icon.

I don't believe in actual normal usage will burn-in those icon, it is high possible the person purposely turn on the screen forever not sleep and let it be there.

After 2 years is make sense, but few days or a month is not make sense. This is like purpose torture to make it burn-in.