We have both manual and automatic equipment. If this were an order for more than a dozen shirts, we would print it on our automatic.
If I have an order for 36 shirts, we would P-F-P with just one screen. This would require the shirt making two revolutions around the press.
The additional printing time would be more than offset by not having to make a white under base screen (artwork, positive, exposure time and related costs, registering two screens, reclaiming a second screen, etc.)
If the order were for 200 shirts, then making a white under base screen and it's related costs would be more efficient, productive and profitable than running each shirt around the press twice (and effectively doubling the production time).