A line plays in the background that is contradictory to the original trilogy. It suggests that the galaxy always knew about Palpatine’s Force abilities.
Remember when Rey reminded Luke of his redemption of Vader and his immediate response after that “he became a legend” (the inference being that the galaxy learned of it post-OT)? Think of it in that way.
This thinking would work, but the problem is that the line specifically says the word always. If that word weren’t included in the line, there would be no issue. But with it there, the idea is that people have, well, always considered the idea that Palpatine is trying to cheat death. Since he was considered a normal dude until post-ROTJ, this line is blatantly false unless you wish to contradict established canon.