Why Pressure Cooker Mac and Cheese Works

I was so excited to see you guys post the recipe for instant pot mac and cheese! I've been following a similar recipe for several years and it's consistently produced the best mac and cheese I've ever had. I love some of the elements of yours and will try it too. But now that you've published a recipe for it, I finally have a venue for asking the question that's eaten away at me :-)

Why does this work?

I completely understand speeding up cooks that would normally take all day. Pressure makes a huge difference for something that would normally be low and slow. But boiling dried pasta is one of the easiest things you can do in the kitchen. What does cooking it under pressure achieve?

Thank you!