My thought is that Puzo, at least, was trying to present as something of a mechanical man, a robot that served Vito but wasn't a fully functioning person.
I came to somewhat the same conclusion in a thread I started in the "Novel" board a long time ago, Pete:
http://www.gangsterbb.net/threads/ubbthreads.php?ubb=showflat&Number=900431&Searchpage=1&Main=35815&Words=%2BDid+%2BTom&Search=true#Post900431
Also from the flashback Tom says; "Pop had to pull a lot of strings to get your deferment".
Good catch, Gud! Perhaps Puzo and FFC, taking pity on Tom, threw him one "family intimacy" for the last time we see him in the Trilogy.
