There are expectations in Volm relationships that are very different from the ones in human relationships, Cochise is learning. While the Volm are the more reserved species, they do make an exception when they are attempting to secure a mate.
Humans do the opposite- he has witnessed Hal and Maggie declare their affection with merely three words after speaking at length about trivial things. He is braced for the confused disappointment should Tom follow suit. He is an alien; it is not his fault that he does not know the Volm way.
When it does happen, Tom's eyes bright and his fingers shaking against Cochise's cheek, Cochise is surprised to find that he is not disappointed. There are whole caverns of meaning beneath those three words that Cochise had never guessed at. While part of Cochise still wishes that Tom would express himself as a Volm mate would, he is content with Tom's short I love yous, said with his characteristic tender care.