Does the construction of an object through a class variable always need the parent class to have a constructor?

A bit of a convoluted question, I know, and I'm sure someone is at hand to simplify it to its basics.

Consider the following code:

TTestClass = class
public
end;

TTestClassDescendant = class(TTestClass)
public
  constructor Create;
end;


implementation

procedure TForm1.Button1Click(Sender: TObject);
var tc: TTestClass;
begin
  tc := TTestClassDescendant.Create;
  tc.Free;
end;

{ TTestClassDescendant }

constructor TTestClassDescendant.Create;
begin
  ShowMessage('Create executed')  // this gets executed
end;

The Create procedure gets executed properly.

Now consider following code:

TTestClass = class
public
end;

TTestClassDescendant = class(TTestClass)
public
  constructor Create;
end;

TTestClassClass = class of TTestClass;

implementation

procedure TForm1.Button1Click(Sender: TObject);
var tc: TTestClass;
    tcc: TTestClassClass;
begin
  tcc := TTestClassDescendant;
  tc := tcc.Create;
  tc.Free
end;

{ TTestClassDescendant }

constructor TTestClassDescendant.Create;
begin
  ShowMessage('Create executed')  // this does NOT get executed
end;

The Create procedure of the descendant class does not get executed anymore.

However, if I introduce a constructor in the parent class and override it in the descendant class, it does get executed:

TTestClass = class
public
  constructor Create; virtual;
end;

TTestClassDescendant = class(TTestClass)
public
  constructor Create; override;
end;

Pardon me if I'm overlooking the obvious, but shouldn't the constructor code in that second block of code be executed when the construction occurs through a class variable, just as it is when it is called through the class identifier itself?