That (and other foamy, bubbly, and similar things) are things they tell you to let the pressure release naturally, otherwise, you could get the valve clogged with foam. One thing I've made up for this with, when cooking lentils, is cook it less time (depending on the variety), but let the 12 or 15 minutes of pressure release make up for it. Things like grits, and other "porridge" type things I set for 1 minute, but the time going up to it, and the release time, makes up for it. They could be done as quickly in a saucepan, but stirring constantly - with the IP, I put it in, and forget about it, until the valve drops.