It's been well known for awhile now that it's his preferred setup.
He seems to want as much stability as possible; while being as minimal as possible; with as little fuss to install and keep up to date as possible. Fedora meets those needs. Gnome is Fedora's main concentration.
Oh I didn't know Gnome was the official flavour now, last time I paid attention it was still KDE
He must not use any gnome extensions.
He explained that in the linked video - Fedora makes it easy for him to test custom kernel builds.