It's not in TCS. It's in HG. TCS is much more of a wargame than it is a role-playing game, so it makes different simplifications to the game universe than HG does.It's not in TCS; TCS is explicit that, in the Campaign rules, yes, indeed, you need a B port to build non-starships, and an A to build starships; no explicit restriction nor enabling is placed on small craft.
Hans