Is presuppositional apologetics a form of circular reasoning?

I know a bit about classical apologetics (e.g the works of Richard Swinburne and W.L Craig) and evidential apologetics (e.g Gary Habermas, Mike Licona). Overall, I think the reasoning is clear. What I found a bit confusing is presuppositional apologetics. Consider this: > You take the teachings of Scripture and act as if they are true > (which, of course, they are), even if they contradict what your > discussion partner is telling you. In this way of apologetics, you > let Scripture tell you what is true about the unbeliever, his > challenges, what he already knows, and the whole conversation. And you > view the whole conversation through the lens of Scripture. > > https://thethink.institute/articles/presupvsevidential I remember learning some methods of proof on Discrete Math class many years ago, and one of them was proof by contradiction . If you want to prove Christianity is true, then start at the assumption that Christianity is false, and see if the consequence support that. So, I wonder if the presuppositional folks are doing circular reasoning. Perhaps I misunderstand something about their approach, though.