I have a friend who was in 10th Special Forces Group.
He explained this situation to me in detail.
A retired military service dog watches over his family.
She is not a pet.
A military service dog is a soldier's partner, it's battle buddy.
They're not leaving it behind.
It's getting on the plane with them, and they are leaving together.
They are a unit.
That's why when you see a police car, with a police dog, it's called a K-9 unit.
I'm not saying we didn't leave dogs, but It's likely those dogs hadn't 'graduated' yet.
It's very sad. When I had down time, I'd go hang out by the LZ at Camp Sullivan and watch the dogs, as I missed mine - GSDs and Mals.