This means there is no preference for the Oobe MD design in Local State. Then the following BT happens:

#0  chromeos::WizardController::ShowNetworkScreen (this=0x2d463d7cbba0)
    at ../../chrome/browser/chromeos/login/wizard_controller.cc:412
#1  0x000055555727b73a in chromeos::WizardController::AdvanceToScreen (this=0x2d463d7cbba0, 
    screen_name="network") at ../../chrome/browser/chromeos/login/wizard_controller.cc:945
#2  0x000055555727b43e in chromeos::WizardController::Init (this=0x2d463d7cbba0, 
    first_screen_name="network") at ../../chrome/browser/chromeos/login/wizard_controller.cc:326
#3  0x0000555557215a02 in chromeos::LoginDisplayHostImpl::StartWizard (this=0x2d463e52aa20, 
    first_screen_name="network")
    at ../../chrome/browser/chromeos/login/ui/login_display_host_impl.cc:563
#4  0x0000555557218407 in chromeos::LoginDisplayHostImpl::StartPostponedWebUI (this=0x2d463e52aa20)
    at ../../chrome/browser/chromeos/login/ui/login_display_host_impl.cc:1097

because the network screen is the resumption screen but there is no prefs::kOobeMdMode set to true in local state.

It seems to me that it would be more robust to have a pref to disable MD rather than one to enable it (even if that means converting from one to another for a very brief moment), because as soon as local state is not saved properly, you will be opted out of MD forever by this:

https://cs.chromium.org/chromium/src/chrome/browser/chromeos/login/wizard_controller.cc?rcl=0&l=323