Placeholders in Form Fields are Harmful

I usually take NNGroup information as sacred but I watched this video where they say that an input should not contain a placeholder on the inside box and while the explanation itself is correct they do not take on a case where you have a label above the input and a placeholder inside but they insist on leaving the input empty.

Are there any studies on this ? I couldn`t imagine a search field without a placeholder or other inputs where you use the placeholder to show an example of the expected user input.

https://www.youtube.com/watch?v=jrigp2L-P-0