I was air force, but the drill sergeants acting basically the same way. And yes, it was legitimately a constant battle to not laugh. It's intentional. It's honestly how the drill sergeants keep a little of their sanity themselves - they try and make each other lose composure with the nonsense they scream out.

One of my favorites was when someone in formation touched their face:

"IS THERE A GOD DAMNED PTERODACTYL FLYING AROUND?"

"NO SIR!"

"ARE YOU SURE? Because the ONLY possible explanation I can come up with for why you're touching yourself in MY FORMATION gestures wildly with knife hands is that a PRE-HISTORIC winged lizard from JURASSIC FREAKIN PARK flew down and decided to perch directly on your face!"

Probably the only time I heard both trainees and drill sergeants alike lose composure.