It seems that the BazelJUnitOutputListener class can handle only up to 4 jupiter @Nested classes for simple tests. This is because with no nesting, there are 3 segments, and since (1) each nested class adds another segment to uniqueId, and (2) the matchTestCasesToSuites_locked method can handle up to 6 nested classes, the method silently handles nested classes until you hit 4, in which case I get the following error:
WARNING: Unexpected test organization for TestIdentifier
[uniqueId = [engine:junit-jupiter]/
[class:<TestClass>]/
[nested-class:<nest1>]/
[nested-class:<nest2>]/
[nested-class:<nest3>]/
[nested-class:<nest4>]/
[method:<testmethod>], ...]