When Iroh was a boy his mother made the tea ceremony their own private ritual.
"Tea," she would say with a glint in her eye- the Lady Ilah of his memory always looked like she was telling a private joke. "Is one of the three necessities of life."
Iroh remembered how earnestly he had nodded at her. "Fire, honor, and tea."
He was rewarded with a smile. Father often said it was the reason he fell in love with her. He saw that smile and decided he had to have it. There were many lazy afternoons where Iroh would lean against her, even as Ilah went back to the work of ruling a country, and think how lucky he was to have inherited something that permanent.
His mother would have glared holes into the hull of the ship to see him now, standing against the wind, offering calming tea to a young man pacing too fast to hear him. Traditionally a man Iroh's age is the one who should be served. It is not Zuko's fault he doesn't know the rituals. Ozai never saw the point in teaching these delicate things, Zuko will not allow himself any moments of stillness now to learn, and Iroh had-. Well. There are plenty of reasons she would be disappointed in all of them.
Iroh finds he has no space to wonder what he would have done if his loving parents were still alive to see the man he had to become.
If he had died in battle Lady Ilah would have clutched at Azulon's arms until she drew blood and told him to avenge her oldest son. She was a great advocate of the war and of revenge.
He does not want to know what she would think of his behavior. He does not want to know what she would think of Ozai's behavior. There is a possibility she would be more concerned by the rudeness than the scar on his nephew's face.
He has to remember their disappointment is for the best.
That doesn't mean Zuko doesn't need the calming tea.
It is the last solace of the old man- to give his nephew the heart of the memory and leave the people who were in it behind.
It has been a long time since he's seen Zuko smile. All of this has become a private ritual too.