Although pick block is a feature on this new version, unlike the old version of Minecraft, it doesn't work in Survival. Although it shouldn't give me whatever I want, for example pick blocking an enderman shouldn't give you its spawn egg in survival, using pick block on something that you do have in your inventory, for example wood, should take that out of your inventory and swap it with the item in your hand. This is how it works on the old Minecraft and I thought it would work like this on the new version of Minecraft as well, but it only works in Creative.