You’re obviously neither a writer, a photographer, a video editor or a music producer then."Experts say you are wrong."
That statement is as worthless as yours. What power users? Where or when did they agree with you?
No, I never use the full screen mode on my Apple notebook. My screen hasn't the size of a post stamp, I'm neither blind as a mole, nor do I have the attention span of an toddler on caffeine, so I can work just fine this way and don't get fatally distracted by a second window on my screen.
On a laptop, full screen is usually necessary in these professions.