I think I misread the statement. I thought it referred to professional photographers. I didn't believe it. LOL!!
Most professionals probably do use auto modes.
Auto modes are usually not NECESSARY, but they do increase the speed and automation of your shots, which is often important in a highly competitive or fast-paced environment.
Think about what you do when you're in manual mode. 95% of the time (not including studio lighting), if you're in manual, you are just trudging through a bunch of robotic, automatic motions that don't require very much or any intelligent thought. Usually, you will choose some variable that is important to the shot, like shutter for action or aperture for landscapes first. Then, you look at the little indicator in your viewfinder, and you adjust it until it is in the middle (or +1 -1 whatever) using the other variables at your disposal.
Why spend time doing robotic things that are always the same? As an artist, my time is not best spent clicking a dial in an indicated direction until a screen says I should stop clicking. That's the sort of mindless step-following that a computer could do just as well and more quickly than me.
So... why not
LET the computer do it just as well and more quickly? That gives me more time and brainpower to devote to artistic decisions.
Manual is still crucial sometimes, like when you have fixed lighting, especially flash lighting, that is going to remain constant throughout a shoot. Then you should be using manual to make the shoot look internally consistent and to ease post processing.
But any time when you find yourself mindlessly adjusting each shot based on what the dial tells you, and are not overriding it for any artistic reason, you could generally speed yourself up by using one of the automatic modes. Which is exactly what a lot of professionals are going to do.
Others may just always use manual. Usually these are pros who were around before auto modes and just aren't used to them. For them, it might not be worth it to relearn (and it could screw up their consistent style, which might hurt business, even), but for you if you're just starting out, it will almost certainly be worth it to learn to use all the tools available.