They are assessed in every part of an interview because every part of being interviewed showcases your presentation and communication skills.

Hence the advice in the article to actually practising interviewing, and why the article does not focus on whiteboard quizzes.

If I was going to judge dev interviewees solely on presentation and communication I'd have hired FEWER people than I have using algorithm questions as well.

If you're junior, and you can't tell me anything interesting about the work you've done in the past, but can at least write some code quickly to solve some sample problems, you've at least shone something.

If you're pretty experienced, though... not having much you can talk in depth about is a bigger flag.