Fragment replace() operating differently to remove() + add()

According to the Android docs:

replace() is essentially the same as calling remove(Fragment) for all currently added fragments that were added with the same containerViewId and then add(int, Fragment, String) with the same arguments given here.

However my code says otherwise.

My app has 1 activity and multiple fragments. It also has a BottomNavigationView with 3 tabs (Options, Game, Leaderboards).

When the MainActivity is initialised, 3 fragments are added to the container FrameLayout MainActivity. Immediately after being added, 2 fragments are hidden which leaves 1 shown on the screen (the opening fragment).

MainActivity.kt

override fun onCreate(savedInstanceState: Bundle?) {
    val transaction = supportFragmentManager.beginTransaction()
    transaction.add(R.id.fragment_layout, firstFragment, "Opening")
    transaction.add(R.id.fragment_layout, OptionsFragment(), "Options")
    transaction.add(R.id.fragment_layout,LeaderboardsFragment(), "Leaderboards")
    transaction.commitNow()
    val transaction2 = supportFragmentManager.beginTransaction()
    val options: androidx.fragment.app.Fragment = supportFragmentManager.findFragmentByTag("Options")!!
    val leaderboards: androidx.fragment.app.Fragment = supportFragmentManager.findFragmentByTag("Leaderboards")!!
    transaction2.hide(options)
    transaction2.hide(leaderboards)
    transaction2.commitNow()
}

From here on out, each fragment that isn't OptionsFragment() or LeaderboardsFragment() is swapped out via replace().

OpeningFragment.kt

transaction?.replace(R.id.fragment_layout, playerDetailsFragment, "Add Player")
transaction?.commit()
gameString = "Add Player"

OptionsFragment() and LeaderboardsFragment() are put into view by being selected from the bottom nav, which then hides every other fragment except for the one selected (e.g if Options is selected from bottom nav, then every fragment is hidden except for OptionsFragment()).

MainActivity.kt

override fun onNavigationItemSelected(item: MenuItem): Boolean {
    val fragmentTags = arrayListOf("Opening", "Leaderboards", "Options", "Add Player", "Question", "Location", "Game Over")
    val transaction = supportFragmentManager.beginTransaction()
    val selectedFragmentTag = when (item.itemId) {
        R.id.action_leaderboards -> "Leaderboards"
        R.id.action_options -> "Options"
        else -> {
            gameString 
        }
    }
    // Selected Fragment
    val selectedFragment: androidx.fragment.app.Fragment? = supportFragmentManager.findFragmentByTag(selectedFragmentTag)
    for (fragment_tag in fragmentTags){
        // Hide every Fragment that has been added and isn't the selected Fragment
        val fragment = supportFragmentManager.findFragmentByTag(fragment_tag)
        if (fragment != null && fragment != selectedFragment) {
            transaction.hide(fragment)
        }
    }
    transaction.show(selectedFragment!!)
    transaction.commit()
    return true
}

This method doesn't work. However - if I use remove() and add() instead of replace(), then it works fine:

OpeningFragment.kt

    val opening = fragmentManager?.findFragmentByTag("Opening")
    transaction?.remove(opening!!)
    transaction?.add(R.id.fragment_layout, playerDetailsFragment, "Add Player")
    transaction?.commit()
    gameString = "Add Player"

Any idea why this is?

from Fragment replace() operating differently to remove() + add()