At 6:30, there is a comment about UPROPERTY being required even if the list of specifiers is empty.
It should be noted that with UE5, Epic also recommends to use TObjectPtr rather than raw pointers:
UPROPERTY()
TObjectPtr<UUserWidget> HUD;
This allows UE to track when the object is used when debugging, and for safety, it also ensures that the pointer is always initialized