This part makes no sense. The empire has fought the crystal lifeforms many times. These soldiers in particular, being stationed at a defensive line exclusively dealing with such enemies, should know first hand what the small ones are capable. A decision that would put the entire fleet in danger...
I stick my finger in my pets or friends mouth every time they yawn next to me. They hate it but it's hilarious. Accidentally taught my dog to move her head away from me during yawn and instead of curling her tongue forward, she hides it to the side. Very weird.