Sorry for the untimely response.
The page you refer to is a Portfolio Template layout Page.
It is a page, with the selected template portfolio and layout Checkers
That would load your Portfolio posts in the layout checkers.
The portfolio archives, such as this one, doesn’t have a settings page where you can select which category, I will pass this on a feature request, as I find it myself a very valid setting to have.
Thank you for your feedback.