@FernwoodI read somewhere, and then promptly forgot all the technical jargon, that's when you steam eggs, the membrane adheres to the shell and makes them easy to peel. When you boil them, the membrane pulls away from the shell and sticks to the egg. I would imagine that when you poke the hole that this interferes with that action of the membrane. As @chromedomesaid, the pressure pushes the moisture inside.
After I read this little tidbit, I always steamed eggs instead of boiling them and I have never had a problem with the shell sticking. The instant pot is a natural for hard boiled eggs and I love it.
I have occasionally had an egg crack when I cooked them right out of the refrigerator. To overcome this, I put them in my perforated stainless steel bowl on a trivet and heat the water on saute, (shut off the instant pot) close the lid and let them sit for about 10 minutes before I steam them. If I want to make potato salad, I cut medium sized potatoes in half and lay them on top of the eggs. I just use the 5 x 5 x 5 method. It's about 5 minutes to come to pressure, 5 minutes cooking time and 5 minutes NPR. Then I take them them out and put them in ice water. After about 4 minutes, I crack the shells all over and let them set few minutes more. Then the shells will slip right off.
