DZ brings up a good point. Are we even certain that the Sith wayfinder illustration is from the Jedi texts and not just Luke’s own notes he happened to keep with them?

That would make the most sense seeing as how they are the ancient Jedi texts and should predate the Sith Order by a great deal. And it lines up with Rey’s dialogue in the scene with Leia: “Luke searched for it for a long time. He nearly found it. There are ciphers here I can’t read, but he said to get there you need one of these. A Sith wayfinder.”

Notice how she doesn’t say, “the Jedi said to get there you need one of these.” This was all initiated by Luke. He wrote the ciphers, and ancient Jedi had nothing to do with Sith wayfinders.

What I’m trying to say here is that if we want the ancient Jedi texts themselves to actually be seen and do something for the plot, we need the new illustration. Otherwise, we get a reference to the texts but no visual of them. And, as DZ pointed out, it makes the most sense for Rey to search for answers about her inner darkness in the ancient texts rather than Luke’s private journal.