The concept of the "Backrooms" comes from internet folklore and creepypasta stories, describing an endless maze of empty, monotonous office-like rooms. While the lore surrounding the Backrooms is largely centered on themes of isolation, existential dread, and the bizarre, there are various interpretations and expansions of the mythos. Some stories might incorporate elements of cannibalism as part of horror or survival scenarios, but this is not a universally accepted aspect of the Backrooms lore.
Ultimately, different creators contribute unique elements to the Backrooms narrative, so themes like cannibalism can vary depending on the specific story or interpretation. However, it's not a foundational aspect of the original concept.