Well if they had just watched ROTS, the Jedi purge would be fresh in their mind. So in that sense, it works. But as a stand alone, I can see what you're saying about it being confusing to a new person. Good point.
It works so perfectly as a bridge between III/IV

It makes both movies even better too.
Tarkin was on that Deebo shyt, no wonder Vader respects him.
But when he leaves the room, Krennic be talking shyt again

I'm no Star Wars person so i don't know. 
another hit
on them right now


in the theatre at those last two scenes