bottomNavigationBar is showing labels when showSelectedLabels and showUnselectedLabels is set to false (Flutter)

Was messing around with the bottomNavigationBarTheme and noticed that the label was showing on the selected item even though showSelectedLabels was set to false. Is this a bug or am I missing something? This behavior only holds true as long as the property is declared in the ThemeData when moved to the bottomNavigationBar it behaves as expected.

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'app',
      themeMode: ThemeMode.dark,
      darkTheme: ThemeData(
        brightness: Brightness.dark,
        primarySwatch: Colors.blueGrey,
        canvasColor: Color.fromRGBO(52, 58, 70, 1),
        bottomNavigationBarTheme: BottomNavigationBarThemeData(
          selectedIconTheme: IconThemeData(
           color: Color.fromRGBO(113, 124, 152, 1),
           size: 28,
          ),
          unselectedIconTheme: IconThemeData(
            color: Color.fromRGBO(196, 201, 212, 1),
            size: 28,
          ),
          type: BottomNavigationBarType.fixed,
          showSelectedLabels: false,
          showUnselectedLabels: false,
        ),
        cardColor: Color.fromRGBO(52, 58, 70, 1)
      ),
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  HomePage({Key key}) : super(key: key);

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  int _selectedIndex = 0;

  void _onItemTapped(int index) {
    setState(() {
      _selectedIndex = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('appbar'),
      ),
      body: Center(
        child: Text('Text here'),
      ),
      bottomNavigationBar: BottomNavigationBar(
        items: const <BottomNavigationBarItem>[
          BottomNavigationBarItem(
            icon: Icon(Icons.access_time),
            title: Text('a'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.view_day),
            title: Text('a'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.equalizer),
            title: Text('a'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.notifications_active),
            title: Text('a'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.account_circle),
            title: Text('a'),
          ),

        ],
        currentIndex: _selectedIndex,
        onTap: _onItemTapped,
      ),
    );
  }
}