When QQuickTextInput is accepted or loses focus, it does:

    if (hasAcceptableInput(m_text) || fixup()) {
        // ...
    }

Notice that it calls QQuickTextInputPrivate::hasAcceptableInput(). Unlike the public QQuickTextInput::hasAcceptableInput() that returns a boolean value, the private version returns a ValidatorState instead. It never calls fixup() when the validator reports that it's in "intermediate" state, because the value of IntermediateInput is 1.