I think this supports his argument. Having to research desktop environments to decide which is optimized for the potential problems a new user may face, then finding a distro that packages that DE is quite frankly too much for the average user.
I’d argue between 3% and 5% of PC users are willing to research and experiment to find the flavor of Linux that truly works for them.
Linux has come a long way, I still remember using Gentoo as a daily driver and seeing Linux cross 1% of desktop share, but the average desktop user doesn’t know the difference between a kernel and a colonel, and they don’t want to.