The uke is a masochist and submissive person who doesn't understand what he is and experiencing things for the first time, without really understanding what ir why he enjoys it and wants more.
So no, right they don't have a safe word because they quite literally didn't know that and they're still learning. I do hope that they will eventually stop to talk about it, maybe look for information tô figure it out and finally decide on a safeword but, it does makes sense why, right now, they don't have one.
Sorry, I made a few typos but I hope it still makes sense. I tried to explain since you seemed confused, I hope that helped a little. ヾ(❀╹◡╹)ﾉ~
Shouldn't they have a safe word damn