I looked up some recipes for pasta al'arrabiata, and one part I find a bit confusing is that most of them finish cooking the pasta in the sauce. So you cook the pasta separately until it's almost done, and then mix it with the sauce and finish cooking. I'm used to simply cooking the pasta and the sauce each for themselves, and only then mix them.
I'm an inexperienced cook, and this part adds some complications where I'm wondering if they're worth it or if I should simply cook the pasta and the sauce separately as usual. I'm comfortable with cooking the pasta alone to something resembling al dente, but mixing them both just before they're finished and then cooking both together makes this more difficult. I also usually use a rather small pot for the sauce, so I'd have to adapt that as well.
So, I'm wondering what the purpose of this step is, and whether I should just cook sauce and pasta entirely separately.