If you never heard those concepts, they are hard to grasp. It is not a fake user. It is just a different profile to use, to play potentially unverified and amateur made games. I think it is telling, that the itch app even offers this feature. Maybe there were other reasons, or they just implemented it, because, why not. It is rather easy to implement, and it does kinda protect the main profile from shenanigans an amateur might have done. Some horror game developers try "clever" things, to spook the player.
Note: you do not need to use that feature. But maybe follow the advice you cited. Do not download and play the newest things, when they are new. They are mostly unfinished anyways, and full of bugs.