Contradictory statements about signal's return type

One document says "Signals and slots can have return types, but signals or slots returning references will be treated as returning void." (https://doc.qt.io/qt-6/moc.html#signal-slot-return-types-cannot-be-references)

But another one says "Signals are automatically generated by the moc and must not be implemented in the .cpp file. They can never have return types (i.e. use void)." (https://doc.qt.io/qt-6/signalsandslots.html#signals)