Cannot inherit from GameMode and change default pawn class

Hello !
It seems that if I have a GameMode C++ class, defining its DefaultPawnClass, and I inherit from it in a Blueprint, altering the default pawn class of this one will have no effect at all. I tested it by making this tutorial: Using Spring Arm Components in Unreal Engine | Unreal Engine 5.2 Documentation, but starting from a 3rd person C++ template.

The only thing I changed was, instead of “In the World Settings window, under Selected GameMode, click the Default Pawn Class and change it to MyCharacter.”:

  • Create BP class based on the C++ 3rd person game mode,
  • In the World Settings window, set Game mode override to My3rdPersonGameMode
  • Click the Default Pawn Class and change it to MyCharacter.

And the result is that my pawn is still the one defined in the C++ class, and not MyCharacter.
Am I doing things wrong here, or is it a bug ?