From my experience, if the crust is not "sealed" this can lead to your lemon curd seeping into the cracks and the crust rising. Believe me, this happened so many times to me when I was testing this recipe. Basically what happens is when the crust is baking, it shrinks and pulls away from the edges of the pan. Once the crust comes out of the oven, use a fork to gently poke holes all over the top (without going all the way through to the bottom). Then take a rubber spatula and gently press the crust back towards the edges of the pan. Anywhere that I notice it had pulled away from the pan, I gently push it back so that there is no crack. That way when you pour the lemon curd over top, it won't sink to the bottom through the cracks around the edges.