I can conform this behaviour in janusgraph-0.6.2, with the inmemory backend with graph.set-vertex-id=true and the graph from https://lists.lfaidata.foundation/g/janusgraph-users/topic/merged_query_using_logical/97516152

The same behaviour is seen in janusgraph.0.6.3.  Can you report this as an issue at: https://github.com/JanusGraph/janusgraph/issues ?

Best wishes,   Marc