Nice playthrough bro! (I already watched it before you posted this)
Yeah you discovered the secret ;) Also on the boss, it wasnt a bug, you killed the bird right before it was gonna kill you, it just doesnt die immediately, it has a death state for about 15 seconds, thats why it wasnt moving.
Being able to shoot while dead is a bug but im leaving it in cause its hiilarious. Thanks for playing!