This concept of universal relation strongly reminds me ideas from Datomic database where all entities are described as changelog which will fit in table with columns "entity-attribute-relation-timestamp-operation-type"
Datomic's approach is more like a temporal log of facts, it's not trying to maintain universal join consistency across all possible paths. The EAV model lets you treat everything as "facts over time" (Datomic's strength yes) instead trying to make every possible join path consistent