If you are recommending a first time Linux user a distro, the goal isn’t to find the perfect one tailored for them, the goal is to get them to use Linux and not have a bad experience, putting a bunch of upfront conditions on choice is overloading
Distro hoping can happen later
I think the obsession part you are referring to isn’t their love for Mint or them regarding it as the best distro. It’s like someone asking which direction they should take to drive somewhere, there’s a sea of people responding with different routes with tiny differences and the Linux Mint response would be “Whatever the GPS decided”
Desktop Environment, the software that controls the windows, icons, and menu.
Their comment is basically saying the experience of two distros using the same DE will be closer than the same distro using different DEs