This is interesting! I wonder where you got this data? I'm relieved to see there's a lower chance of getting a duplicate, but I wonder how it counts duplicates - do you need to have learned the recipe, or have picked up the recipe? Would it be affected by purchasing a recipe from another player?
But, on the topic of the thread, I wish a DIY recipe would pop out of either a rock, tree, or fishing once a day. Some other way to get them would be great, especially seasonal ones. But at the same time, I enjoy the rarity! I don't want it to be too easy to get them.