Failing entity definition:
Workaround #1 (with a superfluous @Column definition):
Workaround #2 (with logical column name usage):
My assumption is that columnNames attribute of @Index annotation are physical values, whereas code in the method
org.hibernate.boot.internal.InFlightMetadataCollectorImpl#buildUniqueKeyFromColumnNames starting on the line 2013 works with it as if it were logical values.