I got this by accident on a failed run of mine.

What's the glitch? Is it the turnaround when you broke open the secret?

No, once I broke the secret, I bounced off the wall, and the pirate left me alone like you would if you entered the secret. In this case, the pirate left but I didn't enter the secret and you can see the pirate's bomb markers do not appear after he leaves and you can see his leave animation once it happens as well. even for the markers that were still there, the bombs didn't come down.

Now I see. Perhaps the trigger volume for the pirate going away was a bit larger than the secret's hitbox.

intresting