At present, if moc has any special handling of Q_DECLARE_FLAGS(), it relies on the use of that macro. However, that macro is only needed because Q_NO_TYPESAFE_FLAGS can switch between it being a typedef to QFlags<Enum> or to uint; and it is surely no longer necessary to support the latter option. So the Q_NO_TYPESAFE_FLAGS is no longer defined anywhere and there is no good reason not to use typedef QFlags<Enum> Flags or using Flags = QFlags<Enum> overtly in the source code, in place of Q_DECLARE_FLAGS(Flags, Enum). Therefore moc needs to recognise all three forms equally, rather than depending on the macro-form.
If moc either pays no attention to this macro, or already does recognise all three forms, there is of course nothing to do here; however, a code review elicited the observation that using the non-macro forms might fall afoul of moc not recognising them.