I don't think there's a problem with materializing fake games, You can even refer to the magazine you do in this jam as a basis for the art direction, story and everything thats not directly related to gamefeel.
Playing devils advocate, fake games can sometimes sell tedious, boring or annoying elements as cool interesting elements that may become hurdles once you try to make them fun or interesting to the player. Example, Your magazine describes a cursed maze inside of a tower that the player has to traverse to continue their quest, and in the guide section it shows this almost impossibly big map of the maze. In those pages, that maze is interesting by its sheer size, but in practical terms, that maze is gonna be a pain to pass thru. My recommendation is to be wary of what could be fun to play and what is better to only see in paper