Erh peobably nobody asked for it to be pvp but making a PVE open space environment would require work. Erh "more" work? Sorry dunno how to make this expansion not look like a lazy "let's plug the holes" attempt.
Simple: make little pvp arenas, don't bother with anything else flying around or any other activities. >> less work and we will be able to say "Yup, in my game I can fly in space... ok not everywhere... ok I can just shoot at other players and that's it... but I can go around small arenas in space, which is in the end...not infinit... and..............T_T".
And that "Been in development for a while" kind of statement just indicates that the crew dedicated to that content was rather small, since most of the assets probably already existed before said development started.
I am rather excited about some more pvp variety. Just don't expect much from that "expansion".
On a second note I will be happy if, proven wrong ^^