Does Makoto Shinkai concentrates on a "distant love" theme for his works?
Yes I think he do. According to interview with ANN, He would like to emphasize on losing someone and may be the influence of Miyazaki's work

Question: Your previous films have had simple themes and complex emotions; what
would you say is the overarching theme of Hoshi o Ou Kodomo?
MS: It's very difficult to put the theme into one word— if it wasn't I
wouldn't have made a two-hour movie! But if you want me to just say
it, I guess that would be how to overcome a sense of deep loss, the
loss of another person.