That might be intentional to make the coincidences more palatable. Also I think it all takes place in a single galaxy.
It never ceases to amaze me just how fast hyperdrive is. The
Millennium Falcon (which, admittedly, manages the upper end of FTL velocities, in-universe) goes from Tattooine in the Outer Rim to a core system (a distance of tens of thousands of light years) in a matter of a few hours at best. Even a lumbering giant like the
Death Star 1 manages the flight from Alderaan to Yavin so quickly that the Rebels only have a few hours at best lead time to prepare their counter-attack before it arrives in-system.
No wonder so many Warsies rag Trekkers off about their "snails' pace" warp drive!
Seriously, almost everything about how Starkiller was presented in
The Force Awakens was messed up. There were lots of better ways
in in-universe technical terms for it to be portrayed. However, there is one thing J J Abrams is good at and that is visual spectacle. He certainly chose the method that
looked most dramatic.