There are takes in porn. There are also set ups, cuts, lights, etc. And of course there's a whole lot of pretending by the performers. Their whole job is to make it look good for the camera.
You know, there are many porn performers who have rules against kissing in their scenes. To them, it's too intimate. That should tell you something about the sex you see on the screen.
All that said, the times I have seen kissing in porn, it usually looks spontaneous. But in the end, porn is about what looks good on camera, not what feels good to the performers.

