This is very important.

Unfortunately, the two examples that you provide (the generic one with ‘placeholder text’ above, and the Apple iOS one with ‘Search’ below) do not meet this criterion.

Placeholder text is not visible when the user clicks or types into the box.

When the user clicks or types in the Search box on iOS, the ‘search’ label disappears.

The Apple iOS example is a ‘survivable error’ — it’s not best practice, but it’s survivable for many tech-savvy users because they use their phones a lot and get used to it.

But survivable errors in frequently used operating systems are quite different from best practice.