Does AppCompatActivity not throw RuntimeException("Stub!") where as Activity does?

I was looking at the decompiled .class files for AppCompatActivity and Activity and noticed that while every method in Activity.class threw a runtime exception

throw new RuntimeException("Stub!");

But the same wasn't true for AppCompatActivity, Is there a reason for the same ?

I know that android.jar only contains stub implementations of android dependencies but isn't the same true for support library classes as well?