The reference is to the use of white phosphorus to drive enemy combatants out of cover where they can be hit easily with high explosive rounds. Hence the burning skull and two separate types of mortar rounds.

That being said, maybe you’re correct in the guess of why it’s included in this photo…

Unless I’m not misinterpreting, it was the chief designer who ‘threw’ (lightly lobbed) a metal ball at the window when it shattered.

They did later throw a ‘baseball’ at it that very suspiciously bounced unlike any baseball I’ve ever seen. Surprise surprise the tennis ball painted like a baseball didn’t break it 😅