It is actually explicit in the OT:
“You, my friend, are all that’s left of their religion.” Sure, he’s talking about the Jedi there, but Vader is a Sith and he still talks about him in that way. He’s basically saying he’s the last force user. And Tarkin is a high-ranking individual in the Empire!
I’ve fixed the audio up a bit: https://youtu.be/vDvO06C6gxk
It’s funny that you call this change abrupt because you could say that about just about everything in this movie. You’re right to a certain extent though, I would prefer to remove her grabbing the book entirely. I’m just not skilled enough to do that unless somebody has some basic footage of the crowd I could slot in there for the beginning of Poe’s line to play first.