What I wanted to imply is that Kodaka himself is not so serious about making friends because he has a love interest within the group of girls.
Rika reminds him of the original purpose of the club and she is the only one who takes it serious. And at the end of Vol. 7 Kodaka has a really guilty conscience because of her "Aren't we already friends?" comment.
And about the reply... he will agree because Sena is his only love interest. He was not able to tell her that he loves her because of his anxiety disorder. He was waiting that she confesses to him first.
You remember that Yozora was unable to tell Kodaka that she is Sora? He had to figure it out himself and he had to approach her. This is all related to her social phobia / anxiety disorder. Kodaka has a similar problem. He must be absolutely sure that the other partner loves him also, so he has to be approached first.
My interpretation is completely different because I consider that the author used his knowledge as a former loner to create the characters in this love story (look at the afterword of Vol. 1).