Absolutely true, of course. Some mountains that aren’t difficult in the summer can be torturous in the winter. And any mountain can be dangerous. As an aside, I do love ascending Shasta, one of my favorites in that region.
But, from the reverence, I get the suspicion that this “startup thought leader” who is trying to sell you courses on blog writing saw that Whitney was the tallest in the 48 and climbed it to be able to weave into a story for a blog. Which makes me take the whole thing even less seriously.