Also the line doesn’t make sense at all, like, “you will take booth sabers to Exegol”, yeah, but why? Does Luke knows that Ben Solo would need it? Have you read script? What’s that on the floor? Is that the script?
My takeaway with that line is that it sounds a lot like an appropriately star wars corny/clunky (in the good way) thing that Obi-Wan would say in ROTJ, so I like it for that. And yes, Luke probably knew what was going on with Ben! Since it was Leia’s actions through the force that brought Ben to the good side, who’s to say Luke didn’t know it was going on, and that Ben would hopefully take a saber.
But either way, that line also has that whole “we’ll always be with you” mentality that Luke has; he kind of could mean it in that way.
After saying that, I don’t really have a big argument for keeping it. The line doesn’t add anything, really. But I don’t think it is bad enough to be necessary to just flat out remove it.