Because like this example and this would be real life imagine you returning from the front after months of fighting hoping you have some time to rest and see your family and friends you are shipped out again to the front for months or longer.
Or in daily life you are done with your work you are tired and want to go and now you need to stay because a person was not done with there work. Like it is fine most of the time but in Japan it is a big problem for a lot of office workers.
But in the first case with Tanya, she said she and her squad is good to go. The colonel directly asked her if her troops were fatigued, and she said no. He then asked her directly if shes ok with being redeployed again and she said yes. Wheres the issue here? It makes me think of women that say no to a man and then expects him to read her mind and know she actually meant yes. Or worse, the man actually thinks no means yes and things like rape happen.
In your second example, if you're tired and you don't want to help, then don't? I have no problems with that either, as long as you don't also get uppity and expect others to help you when they are tired.
It all amounts down to the same thing: treat others as you want to be treated. Corollary being treat others the way they've treated you. Help others so that they help you when you need help. Don't expect help from others if you never help them.
If you're a fan of saying things you don't mean, then don't be surprised if misunderstandings happen.